Report on the Radiolaria/Prunoidea

by Ernst Haeckel

Suborder PRUNOIDEA, Haeckel, 1883 (Pls. 13-17, 39, 40).

Definition.—Spumellaria with an ellipsoidal or cylindrical central capsule, prolonged into one axis (sometimes articulate by annular transverse strictures); with an ellipsoidal or cylindrical, fenestrated siliceous shell (often articulate by annular strictures), invariably prolonged into one axis. Fundamental form monaxon, usually with the poles of the prolonged dimensive main axis equal.

The suborder Prunoidea comprises those Spumellaria in which the fenestrated spherical shell appears prolonged into one axis. The geometric fundamental form of the shell, which in the Sphæroidea was a sphere, in this case therefore becomes an ellipsoid, and whilst in the former all axes originally have the same value (Homaxonia), here one main axis is constantly larger than all other axes (Monaxonia). Usually both poles of this main axis are equal (Haplopola); but in some genera both poles become different (Diplopola).

In the Sphæroidea all planes going through the centre of the shell are circular, whereas in the Prunoidea only those planes are circular which are perpendicular to the main axis; all other planes going through the centre are elliptical; the largest of these are the meridian planes, in which is situated the main axis. Commonly all meridian planes are equal, as no transverse axes (or cross axes) are differentiated.

In my Monograph (1862) only very few forms of Prunoidea, such as Didymocyrtis and Spongurus, are described, and the greater part of them are distributed under different genera of Sphæroidea, such as Haliomma and Actinomma. In my Prodromus (1881) I separated them as the family Zygartida (p. 462). But it seems now much more convenient to restrict this term to a particular family and to give a wider extension to the whole suborder under the name Prunoidea (called after the characteristic ellipsoidal form of a plum, or Prunus, with its stone).

The suborder Prunoidea comprises seven different families, of which the Ellipsida constitutes the simplest and the probable common ancestral group. In all Ellipsida the fenestrated shell is simple, and never composed of concentric or twin shells. In their primitive genus Cenellipsis, the whole shell is geometrically nothing more than a simple ellipsoid (Pl. 39, figs. 1, 2). By development of radial spines it passes into Ellipsidium, by development of spongy framework into Spongellipsis. In the greater part of this family large spines are developed on both poles of the main axis of the shell, but sometimes instead of these solid spines, two opposite hollow fenestrated tubes are developed (Pipettella, Pl. 39, fig. 6).

The second family of Prunoidea, the Druppulida, is much richer in different forms than the simple Ellipsida. In this case the ellipsoidal shell is composed of two or three (rarely more) concentric shells. Constantly one or two of these fenestrated shells are enclosed in the central capsule, and may therefore be called "medullary shells"; and one or two (rarely more) lie outside the central capsule, "cortical shells." The inner medullary shells (one or two) are either spherical or ellipsoidal; the outer cortical shells (one or two, rarely more) are always ellipsoidal. All concentric shells are connected by radial beams. In the simplest form of the subfamily, Druppula (Pl. 39, fig. 3), one medullary shell is connected with one cortical shell. By duplication of the medullary shell arises Prunulum (Pl. 39, fig. 4), and by duplication or multiplication of the cortical shell Cromyodruppa (Pl. 15, figs. 1-4) is formed. In by far the greater portion of this subfamily large spines are developed on both poles of the main axis of the cortical shell (Pls. 16, 17), but sometimes also instead of these solid spines two opposite hollow fenestrated tubes are developed (Pipetta, Pl. 39, figs. 7, 8).

A third family of Prunoidea, closely allied to the two preceding families, is the Spongurida, in which we include all Prunoidea with an ellipsoidal or cylindrical, unjointed shell, in which the lattice-work of the cortical shell is transformed into an irregular, siliceous framework. In the simplest form, Spongellipsis, the simple lattice-shell of Cenellipsis is substituted by an external spongy envelope. In other cases (Spongurus and allied genera) the whole cavity of this external spongy shell is distended with a fine spongy framework. The subfamily of Spongodruppida is distinguished by the possession of a simple or double latticed medullary shell; this lies in the midst of the central capsule, and is connected by radial beams (perforating its membrane) with the enveloping spongy cortical shell. The surface of the latter may bear either radial spines, or two opposite strong polar spines, at the poles of the main axis (Pl. 17, fig. 12).

Closely allied to the Ellipsida and Druppulida are two other families of the Prunoidea, the Artiscida and Cyphinida, which differ from the former by a circular constriction in the equatorial plane of the ellipsoidal shell; and in this way assume a characteristic twin form, like a figure of eight. In the Artiscida the shell is simple (as in the Ellipsida), whereas in the Cyphinida it is composed of two or more concentric shells (as in the Druppulida). The simplest form of the Artiscida is Artiscus (Pl. 39, fig. 9), differing from Cenellipsis in the ring-shaped, equatorial constriction. In other Artiscida polar appendages are developed on both poles of the main axis, either in the form of solid, strong spines (Stylartus), or hollow fenestrated tubes (Cannartus, Pl. 39, fig. 10).

The family Cyphinida differs from the Druppulida in the equatorial constriction of the shell, and from the Artiscida in the presence of two or more concentric shells. One or two of these concentric fenestrated shells are enclosed in the central capsule (and therefore may be called "medullary shells"); the others (one or two, rarely more) lie outside of the central capsule (therefore "cortical shells"). The internal "medullary shells" are always spherical or somewhat lenticular, compressed from both sides; the external "cortical shells" have constantly a ring-like constriction in the equatorial plane, and "twin-shells" are therefore like a figure of eight. The simplest form of this subfamily is Cyphanta, composed of a simple medullary shell and a simple cortical shell, the two being connected in the equatorial plane by radial beams. In Cyphonium (Pl. 39, fig. 12) the medullary shell is doubled, and in Cypassis (Pl. 39, fig. 13) the cortical shell likewise. On both poles of the main axis strong spines are often developed (Cyphinus, Pl. 39, fig. 14), or hollow fenestrated tubes (Cannartidium, Pl. 39, figs. 16-19).

The equatorial constriction of the ellipsoidal shell, which characterises the Artiscida and Cyphinida, is repeated or multiplied in the two following families, in the Panartida and Zygartida; in the former we find three ring-like strictures, in the latter five or more (lying in parallel transverse planes); therefore the fenestrated shell is composed in the one instance of four chambers, in the other of six or more; all the chambers form a single series and have a common main axis. All constrictions lie in planes parallel to the equatorial plane of the original ellipsoid; in the centre of the latter constantly lies a double "medullary shell," composed of two concentric, either spherical or lenticular, compressed shells. In all Panartida we call the two inner chambers (on both sides of the equatorial constriction) "proximal chambers," the two outer chambers (on the poles of the main axis) "distal chambers." The four-chambered cortical shell of the Panartida is either simple (in Panartus, Pl. 40, figs. 1-4) or double, with an external mantle (as in Peripanartus, Pl. 40, figs. 5-7). The simplest form of the subfamily is Panartus (loc. cit.). In this case also on both poles of the main axis may be developed solid spines, or hollow fenestrated tubes (Panarium, Pl. 40, fig. 9).

The seventh and last family of the Prunoidea, the Zygartida is most nearly allied to the Panartida, and appears as a further developmental step from that family. Whilst in the Panartida the cortical shell is constantly four-chambered, with three parallel ring-like constrictions, in the Zygartida it is always prolonged and composed of six or more chambers, separated by five or more ring-shaped constrictions, in the middle of which is the equatorial stricture. In the centre of the latter (as also in the Panartida) always lies the double medullary shell, composed of two concentric, spherical, or lenticular shells. The number of the chambers of the cortical shells is commonly six or eight (with five to seven ring strictures), but it often mounts to ten and sometimes to twenty (with nineteen strictures), as in some species of Zygartus (Pl. 40, fig. 13). All the chambers lie in one series, one behind another, with a common main axis. The cortical shell is usually simple (in Ommatocampe, Pl. 40, fig. 10), sometimes double (in Desmocampe, Pl. 40, fig. 12), rarely triple (in Zygocampe, Pl. 40, fig. 13). In all three cases hollow fenestrated tubes may be developed on the poles of the main axis.

The morphological references and the phylogenetic affinities of all Prunoidea are so complex, that they seem to represent a quite natural group; all forms of it may be derived from the common ancestral form Cenellipsis. But a far more difficult question is the manner in which its pedigree may be constructed. The oldest family is probably the simplest, namely, Ellipsida. From this the Druppulida may be derived by production of medullary shells, the Artiscida by equatorial constriction. The Cyphinida can be produced either from the Druppulida by equatorial constriction or from the Artiscida by development of medullary shells. The Panartida appear as further developmental steps of the Cyphinida, by duplication of the chamber number; and the Zygartida as further productions of the Panartida, by increasing the number of the chambers.

The seven subfamilies of the Prunoidea can be arranged in two sections according to the presence or absence of medullary shells. The Ellipsida, Spongellipsida, and Artiscida possess a simple cortical shell, without a medullary shell; they represent the section Cenoprunida. All other families possess medullary shells, and so represent the section Coccoprunida.

Another character, which can be employed in the arrangement of the seven subfamilies in some larger groups, is the presence or absence of ring-like constrictions, by which the cortical shell is divided into chambers. I. The Monoprunida comprise all forms without any constriction, of which the Ellipsida are without a medullary shell, the Druppulida with one or two medullary shells, and the Spongurida with a spongy cortical shell. II. The Dyoprunida contain all forms with a cortical twin shell, or with two chambers separated by one equatorial constriction, of which the Artiscida are without a medullary shell and the Cyphinida have one or two medullary shells. III. The Polyprunida comprise all forms with several (three or more) constrictions, which separate four or more chambers, of which the Panartida have three constrictions and four chambers, and the Zygartida five or more constrictions and six or more chambers.

The Central Capsule of the Prunoidea is originally ellipsoidal (monaxial), and preserves this form in the greater part of the genera. In some groups, where the axis of the ellipsoid is much prolonged, it passes over to the cylindrical form (with hemispherical vaultings on both poles), as in Spongurus and Spongocore, in many Panartida and Zygartida. Very often the ellipsoidal or cylindrical capsule gets annular transverse constrictions, corresponding to those of the enveloping cortical shell (one single, equatorial stricture in the Artiscida and Cyphinida, three strictures in the Panartida, five or more in the Zygartida). In the Cenoprunida (Ellipsida and Artiscida, also in Spongellipsis) the central capsule lies freely in the cavity of the cortical shell, separated from its inner surface by the jelly-envelope; in all other groups it contains a part of the skeleton, the medullary shell and the beams which connect it with the enveloping cortical shell.

Synopsis of the Families of Prunoidea.

A. MONOPRUNIDA. Shell without transverse stricture	$\scriptstyle {\left\{{\begin{matrix}\ \\\\\ \\\ \\\ \\\ \\\ \ \end{matrix}}\right.}$	a. Shell simple, latticed (not spongy), without enclosed internal shells,	1. Ellipsida.
		b. Shell composed of two or more concentric latticed shells (not spongy),	2. Druppulida.
		c. Shell partially or wholly composed of an irregular spongy framework,	3. Spongurida.
B. DYOPRUNIDA. Shell bilocular, divided by an equatorial stricture into two communicating hemi-ellipsoidal shells.	$\scriptstyle {\left\{{\begin{matrix}\ \\\\\ \\\ \ \end{matrix}}\right.}$	d. Shell simple, without enclosed internal shells,	4. Artiscida.
		e. Shell composed of two or more concentric shells,	5. Cyphinida.
C. POLYPRUNIDA. Shell multilocular, divided by three or more parallel transverse strictures into four or more serial cameræ.	$\scriptstyle {\left\{{\begin{matrix}\ \\\\\ \\\ \\\ \ \end{matrix}}\right.}$	f. Shell with three parallel strictures and therefore four cameræ,	6. Panartida.
		g. Shell with five or more parallel strictures and therefore six or more cameræ,	7. Zygartida.

Family XI. Ellipsida, Haeckel, 1882 (Pls. 13, 14, 39).

Definition.—Prunoidea with simple ellipsoidal shell, without equatorial stricture (without enclosed medullary shell); network a simple lattice lamella, not spongy. Central capsule ellipsoidal or cylindrical, without annular equatorial constriction.

The family Ellipsida comprises the simplest forms of Prunoidea, and probably represents the ancestral forms of this whole suborder. The fenestrated shell, which encloses the ellipsoidal central capsule, is a perfectly simple "cortical shell" of the same form, without enclosed "medullary shell." Its form is commonly a regular monaxial ellipsoid; sometimes a little modified by unequal growth of the two poles of the main axis. Two opposite large spines are often developed at these poles, or it may be that instead of these, two hollow fenestrated tubes are present.

The ellipsoidal fenestrated shell exhibits in the regular Ellipsida all the characters of a geometric ellipsoid; one main axis surpasses in length all other possible axes. All sections going through this main axis are "meridian sections," with elliptical periphery; all sections perpendicular to the main axis are "transverse sections," with circular periphery. The largest of these is the equatorial section, which divides the main axis into halves. The diameter of this equatorial plane is the "minor axis" of the ellipsoid.

The proportion of the two axes of the ellipsoidal shell, of the major vertical or main axis and the minor horizontal or equatorial axis, is commonly between 6 : 5 and 3 : 2. In the former case it approaches the spherical shell, from which it is derived; in the latter case it becomes almost fusiform or cylindrical. The network of silex, constituting the shell, is constantly a simple latticed lamella, never composed of concentric shells (as in Druppulida) or spongy (as in Spongurida). The network is often very regular and elegant, in other cases irregular.

The simplest genus among the Ellipsida, and probably the common ancestral form of the whole subfamily, is the genus Cenellipsis, possessing a simple ellipsoidal shell without any appendages. It is derived from Cenosphæra (the simplest spherical shell) by the prolongation of one axis. Cenellipsis passes over into Ellipsidium by the production of radial spines on the surface (corresponding to Heliosphæra). Axellipsis is a peculiar genus differing from Cenellipsis in an axial rod, which corresponds to the minor or equatorial axis. In all other genera of the subfamily both poles of the main axis are distinguished by peculiar polar prolongations, either hollow fenestrated tubes (as in Pipettella) or strong solid spines. Both polar spines are of equal size and similar form in Ellipsoxiphus, unequal in Ellipsostylus. From the latter is derived Lithapium, by reduction and loss of one spine (so that only one remains); Lithomespilus, by production of a bunch of several spines at one pole. In the three latter genera both poles of the main axis are unequal, in all others equal.

The central capsule of the Ellipsida is in all cases ellipsoidal, and occupies the largest part of the shell, being separated from its inner surface by a thinner or thicker jelly-mantle.

Synopsis of the Genera of Ellipsida.

Ellipsoidal shell without polar appendages (neither solid spines nor hollow tubes at the poles of the axis).	$\scriptstyle {\left\{{\begin{matrix}\ \\\\\ \\\ \\\ \\\ \ \end{matrix}}\right.}$	Surface without radial spines.	$\scriptstyle {\left\{{\begin{matrix}\ \\\\\ \\\ \ \end{matrix}}\right.}$	Shell cavity simple, without an axial rod,	122. Cenellipsis.
				Shell cavity with a transverse axial rod,	123. Axellipsis.
		Surface covered with radial spines,			124. Ellipsidium.
Ellipsoidal shell with polar appendages (either solid spines or hollow fenestrated tubes) at the poles of the main axis.	$\scriptstyle {\left\{{\begin{matrix}\ \\\\\ \\\ \\\ \\\ \\\ \\\ \\\ \\\ \\\ \\\ \\\ \\\ \ \end{matrix}}\right.}$	Solid spines of similar shape, at both poles of the main axis.	$\scriptstyle {\left\{{\begin{matrix}\ \\\\\ \\\ \ \end{matrix}}\right.}$	Shell cavity simple, without axial rods,	125. Ellipsoxiphus.
				Shell cavity with a cross of axial rods,	126. Axoprunum.
		Solid spines of different shape, at both poles of the main axis.	$\scriptstyle {\left\{{\begin{matrix}\ \\\\\ \\\ \\\ \\\ \\\ \ \end{matrix}}\right.}$	Two polar spines of different shape,	127. Ellipsostylus.
				A bunch of spines at one pole only,	128. Lithomespilus
				Only a single spine at one one pole,	129. Lithapium.
		Two hollow fenestrated tubes opposite, at the poles of the main axis,			130. Pipettella.

Genus 122. Cenellipsis,^[1] n. gen.

Definition.—Ellipsida with simple ellipsoidal shell, without radial spines and without polar tubes.

The genus Cenellipsis is the simplest and most primitive form, not only among the Ellipsida, but also among the Prunoidea, and it may therefore be regarded as the common ancestral form of the whole family. It corresponds to Cenosphæra among the Sphæroidea, to Cenodiscus among the Discoidea, to Cenolarcus among the Larcoidea. Probably it is derived from Cenosphæra by prolongation of one axis.

Subgenus 1. Cenellipsium, Haeckel.

Definition.—Network of the shell regular, with meshes of equal size and similar form.

1. Cenellipsis primitiva, n. sp.

Proportion of the longer axis of the ellipsoid to the shorter = 3 : 2. Network of the thin wall very delicate and regular, with hexagonal pores. All pores of nearly the same size and form, ten to twelve times as broad as the bars; nine to twelve on the half equator of the shell. Surface smooth.

Dimensions.—Longer axis of the ellipsoid 0.09 to 0.11, shorter axis 0.06 to 0.08; pores 0.01, bars between them 0.001.

Habitat.—Pacific, central area, Station 272, surface.

2. Cenellipsis faceta, n. sp. (Pl. 39, fig. 1).

Proportion of the longer axis of the ellipsoid to the shorter = 4 : 3. Network of the thin wall delicate and regular. All the pores of the same size and form, circular, with a hexagonal frame, twice to three times as broad as the bars; eight to ten on the half equator. Surface smooth or slightly spiny.

Dimensions.—Longer axis of the ellipsoid 0.12 to 0.13, shorter axis 0.09 to 0.1; pores 0.013, bars 0.005.

Habitat.—Pacific, central area. Station 274, surface.

3. Cenellipsis ehrenbergii, Haeckel.

Haliomma (?) cenosphæra, Ehrenberg, 1875, Abhandl. d. k. Akad. d. Wiss. Berlin, p. 74, Taf xxvi. fig. 5.

Proportion of the longer axis to the shorter = 2 : 1. Network of the thin wall regular or subregular. All pores circular, nearly of the same size, without hexagonal frame, three to four times as broad as the bars; eight to nine on the half equator. Surface covered with small thorns.

Dimensions.—Longer axis of the ellipsoid 0.16 to 0.2, shorter axis 0.08 to 0.1; pores 0.1, bars 0.003.

Habitat.—Fossil in the Tertiary rocks of Barbados (Ehrenberg, Haeckel).

4. Cenellipsis circopora, n. sp.

Proportion of the longer axis to the shorter = 5 : 3. Network of the thin wall delicate and regular. All pores circular, nearly of the same size, without hexagonal frame, twice as broad as the bars; fifteen to twenty on the half equator. Surface quite smooth.

Dimensions.—Longer axis of the ellipsoid 0.15 to 0.2, shorter axis 0.09 to 0.12; pores 0.08, bars 0.4.

Habitat.—North Pacific, Station 236, surface.

5. Cenellipsis micropora, n. sp.

Proportion of the longer axis to the shorter = 5 : 4. Network of the thick wall quite regular. All pores circular, without hexagonal frame, very small, scarcely half as broad as the bars; six to eight on the half equator. Surface quite smooth.

Dimensions.—Longer axis of the ellipsoid 0.1, shorter axis 0.08; pores 0.004, bars 0.01.

Habitat.—South Pacific, Station 289, surface.

Subgenus 2. Cenellipsula, Haeckel.

Definition.—Network of the shell irregular, with meshes of different size or form.

6. Cenellipsis heteropora, n. sp.

Proportion of the longer axis to the shorter = 3 : 2 or = 5 : 3. Network of the thin wall very irregular, with polygonal meshes of different size and form (for the most part pentagonal or hexagonal, but also many tetragonal or heptagonal). The largest pores four to six times as broad as the smallest; ten to twenty pores on the half equator; bars between them thin. Surface smooth or somewhat spiny.

Dimensions.—Longer axis of the ellipsoid 0.18 to 0.22, shorter axis 0.1 to 0.12; pores 0.004 to 0.008, bars 0.001.

Habitat.—Indian Ocean, near the Cocos Islands, surface, Rabbe.

7. Cenellipsis maxima, n. sp.

Proportion of the longer axis to the shorter = 3 : 2. Network of the thin wall very irregular, with polygonal meshes of very different size and form, twice to eight times as broad as the bars; fifty to sixty on the half equator. Surface smooth.

Dimensions.—Longer axis of the ellipsoid 0.36, shorter axis 0.25; pores 0.004 to 0.015, bars 0.002.

Habitat.—Equatorial Atlantic, Station 347, surface.

8. Cenellipsis ovulum, n. sp.

Proportion of the longer axis to the shorter = 3 : 2. Network of the thin wall very irregular, with roundish or longish pores of very different size and form. Pores flat, with even margins, thirty to forty on the half equator, twice to six times as broad as the bars. Surface smooth. (This species being observed alive, showed a transparent central capsule of ellipsoidal form, two-thirds as large as the shell.)

Dimensions.—Longer axis of the ellipsoid 0.3, shorter axis 0.2; pores 0.04 to 0.012, bars 0.002.

Habitat.—Indian Ocean, Ceylon, Haeckel; Pacific, central area, Station 266, surface.

9. Cenellipsis infundibulum, n. sp. (Pl. 39, fig. 2).

Proportion of the longer axis to the shorter = 3 : 2. Network of the thick wall irregular, with roundish pores of different size and form. Pores funnel-like, with prominent, irregular, spiny crests between them, their outer aperture three to four times as broad as the inner; twelve to fifteen pores on the half equator. Surface prickly.

Dimensions.—Longer axis of the ellipsoid 0.14, shorter axis 0.11; outer aperture of the pores 0.01 to 0.012, inner aperture 0.003 to 0.004.

Habitat.—South Atlantic, Station 332, depth 2200 fathoms.

10. Cenellipsis oblonga, n. sp.

Proportion of the longer axis to the shorter = 2 : 1. Network of the thick wall irregular, with roundish pores of different size and form. Pores with prominent conical edges, about as broad as the bars; twenty to twenty-five on the half equator. Sometimes each pore is prolonged into a short conical tubulus.

Dimensions.—Longer axis of the ellipsoid 0.22, shorter axis 0.12; pores and bars 0.008 to 0.012.

Habitat.—Pacific, central area, Station 265, depth 2900 fathoms.

Genus 123. Axellipsis,^[2] n. gen.

Definition.—Ellipsida with simple ellipsoidal shell, without radial spines or polar tubes, but with an inner transverse axial rod, which corresponds to the shorter axis of the ellipsoid.

The genus Axellipsis differs from the simple Cenellipsis in a very peculiar character, namely, the presence of an inner siliceous bar marking the minor axis of the ellipsoidal shell. If in some forms of Druppula (e.g., Pl. 39, fig. 3) we remove the central medullary shell and prolong both beams (connecting it with the cortical shell) till they unite in the centre, we shall arrive at Axellipsis. Therefore Axellipsis may be derived in the same way from Druppula as Axoprunum is from Lithatractus, by phyletic loss of the medullary shell.

1. Axellipsis perforata, n. sp.

Proportion of the major axis of the ellipsoid to the minor = 3 : 2. Pores of the shell regular, circular, twice as broad as the bars; ten to twelve on the half equator. Surface smooth.

Dimensions.—Longer axis of the shell 0.12, shorter axis 0.08; pores 0.006, bars 0.003.

Habitat.—Central area of the Pacific, Station 266, depth 2750 fathoms.

2. Axellipsis lobata, n. sp.

Proportion of the major axis to the minor = 5 : 4. Meshes of the shell irregular, roundish, lobed, with three to six indentations (each mesh formed by the confluence of three to six, commonly four or five, smaller pores); eight to nine meshes on the half equator, these being twice to four times as broad as the bars.

Dimensions.—Longer axis of the shell 0.1, shorter axis 0.08; pores 0.007 to 0.01, bars 0.003.

Habitat.—Tropical zone of the Western Pacific, Station 225, surface.

Genus 124. Ellipsidium,^[3] n. gen.

Definition.—Ellipsida with simple ellipsoidal shell, with numerous radial spines on the surface, without polar spines or tubes.

The genus Ellipsidium differs from Cenellipsis solely in the development of numerous radial spines on the surface, and exhibits the same phylogenetic relation to it that Heliosphæra bears to Cenosphæra.

1. Ellipsidium pandanidium, n. sp.

Proportion of the longer axis of the ellipsoid to the shorter = 5 : 4. Shell thick walled, with regular and hexagonal meshes, twice as broad as the bars; eighteen to twenty on the half equator. In each hexagon-corner (between three pores) arises a short, three-sided pyramidal spine, half as long as the equatorial radius, and as thick at the base as a single mesh.

Dimensions.—Major axis of the ellipsoid 0.15, minor 0.12; pores 0.006, bars 0.003; length of the radial spines 0.03, basal breadth 0.006.

Habitat.—Fossil in the Tertiary rocks of Barbados (Haeckel).

2. Ellipsidium datura, n. sp.

Proportion of the longer axis of the ellipsoid to the shorter = 4 : 3. Shell thick walled, with regular, circular meshes, twice as broad as the thick bars between them eight to ten meshes on the half equator. Outer surface of the shell thorny, covered with short, conical, radial spines, which are regularly distributed (one spine between every three meshes), and about as long as the diameter of the meshes. (The shell is similar to the outer shell of Haliomma castanea, Haeckel, Monogr. d. Radiol., Taf. xxiv. fig. 4.)

Dimensions.—Major axis of the ellipsoid 0.12, minor axis 0.09; meshes 0.012, bars 0.006.

Habitat.—Western part of the Tropical Pacific, Station 225, depth 4475 fathoms.

3. Ellipsidium artocarpus, n. sp.

Proportion of the longer axis to the shorter = 3 : 2. Shell thick walled, with regular, circular meshes, separated by deep furrows, which represent a regular, hexagonal framework; on the half equator twelve to fifteen meshes, scarcely broader than the broad bars between them. Outer surface spiny; between every three meshes arises a strong radial spine, twice to three times as long as the diameter of the meshes; the base of the spine is like a three-sided pyramid.

Dimensions.—Major axis of the ellipsoid 0.12, minor axis 0.08; meshes 0.006, bars 0.005.

Habitat.—Central area of the Pacific, Station 268, depth 2900 fathoms.

4. Ellipsidium opuntia, n. sp.

Proportion of the longer axis to the shorter = 5 : 4. Shell thin walled, with irregular, roundish meshes of different size and form, about twice to three times as broad as the irregular, thin bars between them; ten to fifteen meshes on the half equator. Between the meshes arise numerous thin, bristle-like, radial spines, about as long as the shorter radius of the shell. The number of the meshes may be three to four times as great as the number of the spines.

Dimensions.—Major axis of the ellipsoid 0.15, minor axis 0.12; pores 0.006 to 0.01, bars 0.003 to 0.004.

Habitat.—Southern Pacific, Station 284, surface.

5. Ellipsidium echinidium, n. sp.

Proportion of the longer axis to the shorter = 4 : 3. Shell thick walled, with irregular, roundish pores of different size and form, about as large or somewhat smaller than the broad bars; twelve to sixteen pores on the half equator. On the surface, irregularly scattered, twenty to thirty strong, three-sided pyramidal, radial spines, one-fourth to one-half as long as the main axis.

Dimensions.—Major axis of the ellipsoid 0.16, minor 0.12; pores and bars 0.002 to 0.008; length of the radial spines 0.04 to 0.08, basal breadth 0.01.

Habitat.—Equatorial Atlantic, Station 347, depth 2250 fathoms.

Genus 125. Ellipsoxiphus,^[4] Dunikowski, 1882, Denkschr. d. k. Akad. d. Wiss. Wien, vol. xlv. p. 25.

Definition.—Ellipsida with simple ellipsoidal shell, the main axis of which is prolonged at both poles into two strong opposite spines of equal size and similar form.

The genus Ellipsoxiphus was established by Dunikowski (in 1882, loc. cit.) for those simple amphistylous fenestrated shells, formerly united with Xiphosphæra, in which the mathematical form of the shell itself is not a true sphere, but an ellipsoid. It may therefore be derived from Xiphosphæra by prolongation of the axis in which lie both polar spines; but it may also be derived from Cenellipsis by the production of two equal spines at the poles of the main axis.

Subgenus 1. Ellipsoxiphetta, Haeckel.

Definition.—Network of the shell regular, with pores of equal size and similar form.

1. Ellipsoxiphus elegans, n. sp. (Pl. 14, fig. 7).

Proportion of the major axis of the ellipsoid to the minor = 5 : 4. Shell thick walled, with regular, circular meshes, separated by a regular, hexagonal elevated framework. From each hexagon-corner arises (between every three meshes) a short thin spine, about as long as the diameter of a mesh; twelve to fourteen meshes on the half equator, of the same breadth as the bars. Polar spines three-sided prismatic, cuspidate, about as long as the axis of the shell. (This elegant and not uncommon species is remarkable for its variations. By unequal development of both spines it passes over to Ellipsostylus.) In the figured variety (Pl. 14, fig. 7) the ends of the surface spines are connected by a very delicate network, so as to form an outer veil. This may further be separated as a peculiar genus Ellipsoxiphium palliatum.

Dimensions.—Longer axis 0.08 to 0.13, shorter axis 0.06 to 0.11; pores and bars 0.008; length of the polar spines 0.06 to 0.12, basal breadth 0.01.

Habitat.—Pacific, central area, Stations 270 to 274, from 2350 to 2925 fathoms.

2. Ellipsoxiphus flosculus, n. sp.

Proportion of the major axis to the minor = 6 : 5. Shell very thick walled, with regular, hexagonal meshes, eight to nine on the half equator, three to four times as broad as the bars. The inner contour of the meshes is circular, the outer six-lobed (similar to Xiphostylus phasianus, Pl. 13, fig. 9). Polar spines three-sided pyramidal, about as long as the major axis of the shell; their basal thickness equals one mesh.

Dimensions.—Longer axis 0.12, shorter axis 0.1; pores 0.012 to 0.015, bars 0.004; length of the polar spines 0.12 to 0.15, basal breadth 0.015.

Habitat.—Fossil in the Tertiary rocks of Barbados (Teuscher).

3. Ellipsoxiphus fragilis, n. sp.

Proportion of the major axis to the minor = 4 : 3. Shell thin walled, with regular, circular meshes, twice as broad as the bars; ten to twelve on the half equator. Surface smooth. Polar spines cylindrical, at the apex conical, half as long as the major axis.

Dimensions.—Longer axis 0.16, shorter axis 0.12; pores 0.008, bars 0.004; length of the polar spines 0.09, basal breadth 0.008.

Habitat.—South Atlantic, Station 325, surface.

Subgenus 2. Ellipsoxiphilla, Haeckel.

Definition.—Network of the shell irregular, with pores of different size or form.

4. Ellipsoxiphus claviger, n. sp. (Pl. 14, fig. 3).

Xiphosphæra clavigera, Haeckel, 1881, Prodromus et Atlas.

Proportion of the major axis to the minor = 5 : 4. Shell thick walled, with irregular network; meshes roundish or circular, double contoured, of unequal size, twice to four times as broad as the bars; eight to ten on the half equator. Polar spines club-shaped, with prominent edges, about as long as the minor axis; thicker in their middle part than at both ends (differs from Xiphosphæra clavigera by the ellipsoidal form of the shell, and the double length of the spines).

Dimensions.—Longer axis 0.15. shorter axis 0.12; pores 0.007 to 0.015, bars 0.004; length of the polar spines 0.12, thickness in the middle part 0.02.

Habitat.—Central area of the Pacific, Station 272, depth 2600 fathoms.

5. Ellipsoxiphus suessi, Dunikowski.

Ellipsoxiphus suessi, Dunikowski, 1882, Denkschr. d. k. Akad. d. Wiss. Wien, Bd. xlv. p. 26, Taf. v. fig. 50.

Proportion of the major axis to the minor = 7 : 5. Shell thick walled, with irregular, roundish meshes, six to eight on the half equator, twice to three times as broad as the bars. Polar spines nearly cylindrical, blunt, as long as the major axis.

Dimensions.—Longer axis 0.14; shorter axis 0.1; pores 0.018 to 0.023, bars 0.01; length of the polar spines 0.12; thickness of them 0.035.

Habitat.—Fossil in the Alpine Lias, Schafberg near Salzburg, Dunikowski.

6. Ellipsoxiphus parvoforaminus, Dunikowski.

Ellipsoxiphus parvoforaminus, Dunikowski, 1882, Denkschr. d. k. Akad. d. Wiss. Wien, Bd. xlv. p. 26, Taf. v. fig. 51.

Proportion of the major axis to the minor = 7 : 6. Shell thick walled, with irregular, roundish or oval meshes, ten to twelve on the half equator, scarcely as broad as the bars. Polar spines conical, shorter than the minor axis.

Dimensions.—Longer axis 0.14, shorter axis 0.12; pores 0.016 to 0.01, bars 0.01 to 0.02; length of the polar spines 0.1, basal thickness 0.045.

Habitat.—Fossil in the Alpine Lias, Schafberg near Salzburg, Dunikowski.

7. Ellipsoxiphus bipolaris, n. sp. (Pl. 14, fig. 11).

Xiphosphæra bipolaris, 1881, Prodromus et Atlas.

Proportion of the major axis to the minor = 8 : 7. Shell thick walled, with irregular, roundish meshes, twice to three times as broad as the bars; sixteen to twenty on the half equator. Polar spines short and thick, three-sided pyramidal, scarcely half as long as the shorter radius of the shell; surrounding the base of every spine is a circle of eight to nine shorter spines.

Dimensions.—Longer axis 0.08, shorter axis 0.07; pores 0.003 to 0.007, bars 0.002; length of the polar spines 0.02 to 0.03, basal thickness 0.02.

Habitat.—Tropical part of the Western Pacific, Station 225, depth 4475 fathoms.

8. Ellipsoxiphus atractus, n. sp. (Pl. 14, fig. 1).

Proportion of the major axis to the minor = 3 : 2. Shell spindle-shaped, very thick walled, with roundish, very irregular meshes, twice to five times as broad as the bars; eight to twelve on the half equator. The meshes are partly simple, oblong, partly lobed or composed of two to four (commonly three) confluent meshes. Surface smooth. Polar spines very short and thick, shorter than the minor radius of the shell, three-sided pyramidal, with prominent, somewhat contorted edges.

Dimensions.—Longer axis 0.15, shorter axis 0.1; meshes 0.007 to 0.02, bars 0.004; length of the polar spines 0.04, basal thickness 0.03.

Habitat.—Central area of the Pacific, Station 268, depth 2900 fathoms.

Genus 126. Axoprunum,^[5] n. gen.

Definition.—Ellipsida with simple ellipsoidal shell, the main axis of which is prolonged at both poles into two opposite spines of equal size and similar form. Within the cavity of the shell four radial rods arise from its inner surface, two in the main axis, two in the smallest axis, perpendicular to the former; their free inner ends are at the same distance from the centre.

The genus Axoprunum possesses precisely the same shell as the foregoing Ellipsoxiphus, but differs from it in a very remarkable peculiarity. The two polar spines are centripetally prolonged into two internal beams, and perpendicular to these are two other, opposite, transverse beams, marking the minor axis of the ellipsoid. The free inner ends of all four radial rods bear little thickened knobs, and are at the same distance from the centre. It therefore appears as though a central, spherical, medullary shell had been lost, and this gives a strong support to the important hypothesis, that in many Sphærellaria, where the medullary shell is absent, it may have been lost by phylogenetic reduction or retrograde metamorphosis. In this case Axoprunum (and Ellipsoxiphus) would arise from Lithatractus.

1. Axoprunum stauraxonium, n. sp. (Pl. 48, fig. 4).

Shell ellipsoidal, one and one-third times as long as broad, with smooth surface. Network regular, with circular meshes four times as broad as the bars. Two polar spines three-sided pyramidal, half as long as the shell, as thick at the base as a single mesh. Four inner radial beams (lying, two in the major and two in the minor axis of the ellipsoid) very thin, at the central free ends knob-like, thickened. The distance between two opposite beams equals one-third of the minor axis, and indicates probably the diameter of the lost spherical medullary shell. (Three perfect and complete specimens of the same size and shape were observed.)

Dimensions.—Major axis of the ellipsoid 0.14, minor axis 0.11; pores 0.012, bars 0.003; length of the polar spines 0.07, basal breadth 0.012. (Diameter of the lost medullary shell 0.03?)

Habitat.—South Atlantic, Station 338, depth 1990 fathoms.

Genus 127. Ellipsostylus,^[6] n. gen.

Definition.—Ellipsida with simple ellipsoidal shell, the main axis of which is prolonged at both poles into two opposite spines of different size or form.

The genus Ellipsostylus differs from Ellipsoxiphus only in the unequal size or different form of the polar spines, which in the former are equal. This difference does not seem important at first, but in the further development it produces very singular and strange forms. Theoretically it is always important, because the fundamental haplopolar form of the monaxon body becomes diplopolar by this differentiation.

Subgenus 1. Ellipsostyletta, Haeckel.

Definition.—Network of the shell regular, with pores of equal size and similar form.

1. Ellipsostylus ornithoides, n. sp.

Proportion of the major axis of the ellipsoid to the minor = 4 : 3. Shell thin walled, with regular, circular meshes and hexagonal framework between them, like that of Xiphostylus favosus (Pl. 13, fig. 4). Circular pores about as broad as the bars; eight to nine on the half equator. Surface smooth. Polar spines three-sided pyramidal, as broad at the base as a single hexagon; the longer spine as long as the major axis, the shorter half as long.

Dimensions.—Longer axis of the ellipsoidal shell 0.16, shorter axis 0.12; pores and bars 0.006; length of the longer polar spine 0.16, of the shorter 0.08.

Habitat.—North Pacific, Station 241, depth 2300 fathoms.

2. Ellipsostylus avicularis, n. sp.

Proportion of the major axis to the minor = 3 : 2. Shell thick walled, with regular, rosette-shaped meshes, three times as broad as the bars; ten to twelve on the half equator. Every mesh on the outer margin with five to six rounded lobes, as in Xiphostylus phasianus (Pl. 13, fig. 9). Surface smooth. Polar spines sharp edged, thick; the longer straight and equal to the longer axis, the shorter half as long, shaped like a bird's head.

Dimensions.—Longer axis 0.18, shorter axis 0.12; pores 0.015, bars 0.005.

Habitat.—South Pacific, Station 300, depth 1375 fathoms.

3. Ellipsostylus psittacus, n. sp. (Pl. 13, fig. 6).

Proportion of the major axis to the minor = 4 : 3. Shell thin walled, with regular or subregular rosette-shaped meshes, twice as broad as the bars; eight to nine on the half equator; each mesh with three to four rounded lobes. Surface smooth. Polar spines sharp edged, very unequal; longer spine about twice as long as the major axis, somewhat curved; shorter spine scarcely longer than the radius, shaped like a bird's head.

Dimensions.—Longer axis 0.08, shorter axis 0.06; pores 0.01, bars 0.005; length of the polar spines—longer 0.15, shorter 0.05.

Habitat.—Central area of the Pacific, Station 266, depth 2750 fathoms.

4. Ellipsostylus aquila, n. sp. (Pl. 13, fig. 1).

Proportion of the major axis to the minor = 7 : 6. Shell thick walled, with subregular, circular meshes, five to six times as broad as the bars; ten to twelve on the half equator. Surface smooth. Polar spines sharp edged (six-sided?), very unequal; longer spine straight, about equal to the minor axis; shorter spine obliquely inserted, scarcely half as long, shaped like a bird's head.

Dimensions.—Longer axis 0.15, shorter axis 0.13; pores 0.02, bars 0.004; length of the polar spines—longer 0.1, shorter 0.05.

Habitat.—Central area of the Pacific, Station 272, depth 2600 fathoms.

5. Ellipsostylus columba, n. sp. (Pl. 13, fig. 3).

Proportion of the major axis to the minor = 4 : 3. Shell egg-shaped, thin walled, with regular, circular meshes, three times as broad as the bars; ten to twelve on the half equator. Surface somewhat thorny. Polar spines nearly of equal length (equal to the major axis), but of very different form; one straight, pyramidal, and obliquely inserted, the other like a bird's head.

Dimensions.—Longer axis 0.08, shorter 0.06; pores 0.003, bars 0.01; length of the spines 0.09.

Habitat.—South Atlantic, Station 332, surface.

6. Ellipsostylus ciconia, n. sp. (Pl. 13, fig. 8).

Proportion of the major axis to the minor = 7 : 5. Shell egg-shaped, thick walled; the meshes very small, regular, circular, three times as broad as the bars; sixteen to twenty on the half equator. Surface uneven. Polar spines nearly cylindrical, pointed; the smaller obliquely inserted, equal to the major axis; the larger more than twice as long and thick, furrowed at its base. (Compare with this and the allied species Rhabdolithis pipa, Ehrenberg, 1875, Abhandl. d. k. Akad. d. Wiss. Berlin, Taf. i. fig. 27.)

Dimensions.—Longer axis 0.07, shorter 0.05; pores 0.003, bars 0.001; length of the polar spines—longer 0.2, shorter 0.08.

Habitat.—North Pacific, Station 253, depth 3125 fathoms.

Subgenus 2. Ellipsostylissa, Haeckel.

Definition.—Network of the shell irregular, with pores of different size or form.

7. Ellipsostylus megadictya, Haeckel.

Stylosphæra megadictya, Ehrenberg, 1872, Abhandl. d. k. Akad. d. Wiss. Berlin, p. 299, Taf. viii. fig. 13.

Proportion of the major axis to the minor = 5 : 4. Shell thin walled, with irregular, roundish, large meshes, four to five times as broad as the bars; only four to five on the half equator. Surface smooth. Polar spines straight, thin, angular; the shorter equal to the minor axis, the longer four times as large.

Dimensions.—Longer axis 0.05, shorter axis 0.04; meshes 0.01, bars 0.002; length of the polar spines—longer 0.12, shorter 0.03.

Habitat.—Philippine Sea, 3300 fathoms, Ehrenberg.

8. Ellipsostylus gallinula, n. sp.

Proportion of the major axis to the minor = 3 : 2. Shell thick walled, with irregular, roundish meshes, twice to four times as broad as the bars; eight to ten on the half equator. Surface thorny. Polar spines conical, straight; the longer twice as long as the major axis, the minor scarcely half as long.

Dimensions.—Longer axis 0.15, shorter 0.12; pores 0.01 to 0.02, bars 0.002 to 0.004.

Habitat.—North Pacific, Station 253, surface.

9. Ellipsostylus hirundo, n. sp. (Pl. 13, fig. 2).

Proportion of the major axis to the minor = 4 : 3. Shell thick walled, with irregular, roundish meshes, three to five times as broad as the bars; eight to ten on the half equator. The inner aperture of every mesh is fenestrated by a delicate lamella of silex, perforated by six to eight very small circular pores. Polar spines sharp edged, more or less curved, the shorter equal to the minor axis, the longer twice as long.

Dimensions.—Longer axis 0.16, shorter 0.12; pores 0.01 to 0.02, bars 0.003 to 0.006; length of the polar spines—longer 0.24, shorter 0.12.

Habitat.—Pacific, central area, Station 268, depth 2900 fathoms; the same form also fossil in the rocks of Barbados.

Genus 128. Lithomespilus,^[7] Haeckel, 1881, Prodromus, p. 450.

Definition.—Ellipsida with simple ellipsoidal or oviform shell, the main axis of which bears at one pole a single spine, at the other a bunch of several spines.

The genus Lithomespilus differs from the closely allied Ellipsoxiphus in the further differentiation of both poles of the main axis. One pole exhibits only a single polar spine, the other pole a group of several spines, peculiarly grouped together. It differs from the similar Sphæromespilus (Pl. 14, figs. 12, 13) in the ellipsoidal form of the shell.

1. Lithomespilus phloginus, n. sp. (Pl. 14, fig. 16).

Proportion of the major axis of the ellipsoid to the minor = 4 : 3. Shell thick walled, with circular pores of different size, the breadth of which equals that of the bars; twelve to fifteen pores on the half equator. Surface smooth, with the exception of a circumpolar region covered with numerous thick spines of unequal size, which surround the large single polar spine and are curved like a bow against its axis. This larger polar spine is straight, and equals in length the major axis of the shell. The other and opposite polar spine is scarcely one-fourth as long, perfectly simple, very stout, and of a three-sided pyramidal shape.

Dimensions.—Longer axis of the ellipsoidal shell 0.08, shorter axis 0.06; pores 0.002 to 0.006, bars 0.003 to 0.005; length of the polar spines—longer 0.08, shorter 0.02.

Habitat.—Indian Ocean, near Madagascar, depth 1200 fathoms, Smith.

2. Lithomespilus phlogoides, n. sp. (Pl. 14, fig. 17).

Proportion of the major axis to the minor = 5 : 4. Shell very thick walled, with roundish, double-contoured pores of different size and form, twice to three times as broad as the bars; sixteen to eighteen pores on the half equator. Surface smooth, with the exception of a circumpolar region covered with numerous thin spines of unequal size, which surround the large single polar spine and are curved like a bow against its axis. This larger polar spine is straight, and equals half the size of the major axis of the shell; the other polar spine (sometimes double, as in the figured specimen) is much shorter, being scarcely one-fourth as long.

Dimensions.—Longer axis of the shell 0.08, shorter axis 0.065; pores 0.003 to 0.006, bars 0.002 to 0.004; length of the polar spines—longer 0.04, shorter 0.01.

Habitat.—Central area of the Pacific, Stations 270 to 272, depth 2425 to 2925 fathoms.

3. Lithomespilus flammeus, n. sp.

Stylosphæra species, Bury, 1862, Polycystins of Barbados, pl. xi. fig. 3.

Proportion of the major axis to the minor = 4 : 3. Shell thick walled, with irregular, roundish pores, about as broad as the bars; ten to twelve pores on the half equator. Surface spiny. Length of the conical straight spines increasing towards the poles; each polar spine surrounded by a circumpolar group of larger, somewhat curved spines. The larger polar spine equals in length the major axis; the smaller is scarcely half as long. (The figure, given by Bury, is not quite exact; there the spines are situated in the pores, instead of between them. In my specimen the polar spines were not branched.)

Dimensions.—Longer axis of the shell 0.12, shorter axis 0.09; pores and bars 0.004 to 0.006; length of the polar spines—longer 0.12, shorter 0.06.

Habitat.—Fossil in Barbados.

4. Lithomespilus flammabundus, n. sp. (Pl. 14, fig. 14).

Proportion of the major axis to the minor = 4 : 3. Shell thin walled, with irregular, roundish pores, partly simple, partly composed of three to six confluent pores; only six to eight pores on the half equator, twice to four times as broad as the bars. Surface spiny. Length of the conical irregular spines increasing towards the poles; each polar spine surrounded by a flame-shaped, circumpolar area of longer spines; all large spines (also the polar spines) curved or contorted at one pole and much stronger and more numerous than at the other; length variable, often equal to the longer axis.

Dimensions.—Longer axis of the shell 0.12, shorter axis 0.09; pores 0.005 to 0.015, bars 0.003 to 0.005; length of the polar spines 0.1 to 0.15.

Habitat.—Western part of the Tropical Atlantic, Station 347, depth 2250 fathoms.

Genus 129. Lithapium,^[8] n. gen.

Definition.—Ellipsida with simple ellipsoidal or pear-shaped shell; with a single spine only situated at one pole of the main axis.

The genus Lithapium represents a peculiar modification of Ellipsoxiphus; one of the two opposite polar spines disappears by reduction, and in this way only a single spine remains, at one pole of the main axis. For this reason the shell assumes a characteristic pear-shape, and may easily be confounded with some similar Monocyrtida (Halicapsa).

1. Lithapium pyriforme, n. sp. (Pl. 14, fig. 9).

Proportion of the longer axis to the shorter = 6 : 5. Shell thin walled, with regular, circular pores, four times as broad as the bars; six to eight on the half equator. Surface a little thorny. The single polar spines three-sided pyramidal, as broad at the base as one mesh, about as long as the radius of the shell. (In the specimen figured, there was on the opposite pole a little rudiment of the other lost polar spine; it is missing in other specimens.)

Dimensions.—Major axis of the ellipsoidal shell 0.12, minor axis 0.1; pores 0.02, bars 0.005; length of the single polar spine 0.05, basal thickness 0.02.

Habitat.—Central area of the Pacific, Station 266, depth 2750 fathoms.

2. Lithapium halicapsa, n. sp. (Pl. 14, fig. 8).

Proportion of the longer axis to the shorter = 6 : 5. Shell thin walled, with irregular, lobed meshes, six to eight on the half equator, twice to five times as broad as the bars; each mesh composed of two to five confluent roundish pores. Surface a little thorny. The single polar spine pyramidal, as broad at the base as one mesh, one-third as long as the axis.

Dimensions.—Major axis 0.12, minor axis 0.1; pores 0.01 to 0.02, bars 0.002 to 0.006; length of the single polar spine 0.03, basal thickness 0.02.

Habitat.—Central area of the Pacific, Station 270, depth 2925 fathoms.

3. Lithapium monocyrtis, n. sp. (Pl. 14, fig. 10).

Proportion of the longer axis to the shorter = 7 : 6. Shell thick walled, with irregular, lobed meshes, four to six on the half equator, three to six times as broad as the bars; each mesh composed of three to six confluent roundish pores. Surface quite smooth, without thorns. The single polar spine pyramidal, as broad at the base as the largest mesh, half as long as the radius. (This species is closely allied to the foregoing, but differs in the smooth surface and the larger meshes.)

Dimensions.—Major axis 0.15, minor axis 0.13; pores 0.01 to 0.03, bars 0.003 to 0.01; length of the single spine 0.04, basal thickness 0.03.

Habitat.—Central area of the Pacific, Station 268, depth 2900 fathoms.

Genus 130. Pipettella,^[9] n. gen.

Definition.—Ellipsida with simple ellipsoidal shell, the main axis of which is prolonged at the pole into two opposite hollow fenestrated tubes of equal size and similar form.

The genus Pipettella is distinguished from the other Ellipsida by two hollow perforated tubes, which are directed in the longer axis of the ellipsoidal shell and arise from opposite poles of this axis. It may be derived from Cenellipsis by prolongation of both poles of the main axis. As the same peculiar production of two opposite latticed tubuli at the poles of the main axis obtains in nearly all families of Prunoidea (Pipetta, Cannartus, Panarium, Zygartus, &c.), it may possess a peculiar value in this group.

1. Pipettella fusiformis, n. sp.

Shell spindle-shaped, thin walled, the two opposite tubes being conical and not longer than the short transverse axis of the ellipsoidal shell; no sharp demarcation between them. The two axes of the ellipsoid bear the proportion of 3 : 2. Network of the shell and of the tubes equal, delicate, regular, hexagonal, with circular apertures of equal size; fourteen to sixteen on the half equator of the shell. Bars very thin. The shell of this species is similar to that of Cannartiscus amphiconiscus (Pl. 39, fig. 19), but possesses no equatorial stricture and no medullary shell.

Dimensions.—Longer axis of the ellipsoid 0.18, shorter axis 0.12; length of the tubes 0.1, their basal breadth 0.05; pores of the network 0.01, bars 0.001.

Habitat.—Northern Pacific, Station 244, depth 2900 fathoms.

2. Pipettella tubulosa, n. sp.

Shell ellipsoidal, thin walled, distinctly separated from the two opposite tubes, which are cylindrical, longer than the main axis of the ellipsoid, and one-sixth as broad as the shorter axis. The longer axis of the ellipsoid bears to the shorter the proportion of 5 : 4. Network of the shell and of the tubes equal, regular, with very small circular pores, about as broad as the bars; sixteen to eighteen pores on the half equator of the shell.

Dimensions.—Longer axis of the ellipsoid 0.15, shorter axis 0.12; length of the tubes 0.16 to 0.2, breadth of them 0.02; pores of the network 0.003, bars 0.003.

Habitat.—Western Tropical Pacific, Station 225, depth 4475 fathoms.

3. Pipettella elongata, n. sp.

Shell ellipsoidal, thick walled, distinctly separated from both opposite tubes, which are cylindrical, much prolonged, twice to three times as long as the main axis of the ellipsoid, and one-fifth as broad as the shorter axis. Both axes of the ellipsoid bear the proportion of 3 : 2. Network of the shell and of the tubes irregular with small rounded pores of different size, separated by broader bars (often twice to three times as broad), four to six pores on the half equator of the shell. (This species somewhat recalls Solenosphæra serpentina, Pl. 7, fig. 7; but the tubes are straight, not contorted.)

Dimensions.—Longer axis of the ellipsoid 0.2, shorter axis 0.14; length of the tubes 0.4 to 0.5, breadth 0.03; pores of the network 0.001 to 0.002, bars 0.003 to 0.004.

Habitat.—Central area of the Pacific, Station 271, depth 2425 fathoms.

4. Pipettella prismatica, n. sp. (Pl. 39, fig. 6).

Shell ellipsoidal, thick walled, distinctly marked off from the two opposite tubes, which are longer than its main axis and as broad as one-fifth of it; they are nearly four-sided prismatic, with four strong ribs or edges; these are directed parallel to the main axis, in two meridian planes, perpendicular to one another. The wall of the shell is thickened in the equatorial plane, so as to form a slight stricture on the inside, separating its two halves. Both axes of the ellipsoid bear the proportion of 7 : 6. Network regular, with circular pores, somewhat broader than the bars. The meshes of the shell (fourteen to sixteen on the half equator) are twice as great as those of the tubes, which are arranged in two longitudinal rows between every two ribs (there being eight longitudinal rows on the whole tube). This species is very remarkable for the rudimentary internal equatorial stricture of the shell (transition to the genus Cannartus, Pl. 39, fig. 10), and by the four edges of the tubes, which indicate two of the dimensive axes, the third being represented by the main axis.

Dimensions.—Longer axis of the ellipsoid 0.14, shorter axis 0.12; length of the tubes 0.15 to 0.16, breadth 0.03; pores of the shell 0.008 to 0.01, pores of the tubes 0.004.

Habitat.—Western Tropical Pacific, Station 225, depth 4475 fathoms.

Family XII. Druppulida, Haeckel, 1882 (Pls. 15, 16, 17, 39).

Definition.—Prunoidea with ellipsoidal, latticed (not spongy) shell, composed of two or more concentric shells; a simple or double cortical shell enclosing one or two internal concentric shells (medullary shells), without equatorial stricture. Central capsule ellipsoidal or cylindrical, without annular equatorial constriction.

The family Druppulida differs from the Ellipsida only in the possession of a simple or double medullary shell, which is enclosed in the centre of the central capsule, and connected with the ellipsoidal cortical shell (lying outside it) by radial beams, perforating the membrane of the capsule. The Druppulida exhibit therefore the same relation to the Ellipsida that the Dyosphærida among the Sphæroidea bear to the Monosphærida. The cortical shell may be simple or multiple. The whole fenestrated shell is thus composed of a variable number (two at least) of concentric shells, which are connected by radial beams.

The Medullary Shell—enclosed in the centre of the central capsule—is either simple or double, and composed of two small concentric shells. Their form is either spherical, or ellipsoidal, or lenticular. If the medullary shell be ellipsoidal, the main axis of the ellipsoid is the same as in the cortical shell. Sometimes the inner medullary shell is spherical, the outer ellipsoidal or lenticular. If the medullary shell be lenticular (arising from both poles of the main axis) its vertical axis is also identical with that of the cortical shell (Pl. 39, fig. 5).

The Radial Beams, which connect the medullary and cortical shell, are either developed in all possible directions (Pls. 16, 17), or limited to the equatorial plane, more rarely to the meridional plane. Sometimes the connection is produced only by two opposite beams which lie in the minor or equatorial axis (Pl. 39, figs. 3, 7, 8); more rarely in the major or meridional axis (Pl. 17, figs. 7, 8).

The Cortical Shell is constantly ellipsoidal, rarely with modifications, similar to those which appear in the simple shell of some Ellipsida. As a rule it is simple, rarely composed of two or more (sometimes six or more) concentric ellipsoidal shells (in Cromyodruppa and Cromyocarpus). The outer surface is commonly smooth, more rarely covered with radial spines (in Druppocarpus, Prunocarpus, &c.). In the majority peculiar polar appendages are developed at both poles of the main axis, these being prolongations of them, either in the form of hollow fenestrated tubes (Pipetta, Pipettaria, Pl. 39, figs. 7, 8), or solid strong spines. The two polar spines are either equal in size and similar in form (as in Lithatractus, Stylatractus) or unequal (as in Druppatractus, Xiphatractus, Pls. 16, 17).

The most primitive of all Druppulida is Druppula, with simple medullary shell and simple cortical shell (Pl. 39, fig. 3); Prunulum differs from it only in the possession of a double medullary shell (Pl. 39, fig. 4). From these two genera all other forms of the subfamily may be derived.

The Central Capsule of the Druppulida is constantly ellipsoidal, larger than the concentric enclosed medullary shells, smaller than the surrounding cortical shell; it is separated from the inner surface of the latter by a thinner or thicker jelly-mantle.

Synopsis of the Genera of the Druppulida.

Cortical shell without polar appendages (neither solid spines nor hollow tubes at the poles of the main axis).	$\scriptstyle {\left\{{\begin{matrix}\ \\\\\ \\\ \\\ \\\ \\\ \\\ \\\ \\\ \\\ \\\ \\\ \\\ \ \end{matrix}}\right.}$	Cortical shell simple, ellipsoidal.			$\scriptstyle {\left\{{\begin{matrix}\ \\\\\ \\\ \\\ \\\ \\\ \\\ \\\ \ \end{matrix}}\right.}$	Medullary shell simple.	$\scriptstyle {\left\{{\begin{matrix}\ \\\\\ \\\ \ \end{matrix}}\right.}$	Surface smooth,	131. Druppula.
								Surface spiny,	132. Druppocarpus.
						Medullary shell double.	$\scriptstyle {\left\{{\begin{matrix}\ \\\\\ \\\ \ \end{matrix}}\right.}$	Surface smooth,	133. Prunulum.
								Surface spiny,	134. Prunocarpus.
		Cortical shell composed of two or more concentric shells.			$\scriptstyle {\left.{\begin{matrix}\ \\\\\ \\\ \ \end{matrix}}\right\}\,}$	Medullary shell double.	$\scriptstyle {\left\{{\begin{matrix}\ \\\\\ \\\ \ \end{matrix}}\right.}$	Surface smooth,	135. Cromyodruppa.
								Surface spiny,	136. Cromyocarpus.
Two opposite solid spines, arising from the poles of the main axis.	$\scriptstyle {\left\{{\begin{matrix}\ \\\\\ \\\ \\\ \\\ \\\ \\\ \ \end{matrix}}\right.}$	Cortical shell simple, ellipsoidal.	$\scriptstyle {\left\{{\begin{matrix}\ \\\\\ \\\ \\\ \ \end{matrix}}\right.}$	Medullary shell simple.	$\scriptstyle {\left\{{\begin{matrix}\ \\\ \end{matrix}}\right.}$	Both polar spines equal,			137. Lithatractus.
						Both polar spines unequal,			138. Druppatractus.
				Medullary shell double.	$\scriptstyle {\left\{{\begin{matrix}\ \\\ \end{matrix}}\right.}$	Both polar spines equal,			139. Stylatractus.
						Both polar spines unequal,			140. Xiphatractus.
		Cortical shell composed of two or more concentric shells; medullary shell double; both polar spines equal,							141. Cromyatractus.
Two opposite hollow fenestrated tubes, arising from the poles of the main axis.	$\scriptstyle {\left.{\begin{matrix}\ \\\ \end{matrix}}\right\}\,}$	Cortical shell ellipsoidal.			$\scriptstyle {\left\{{\begin{matrix}\ \\\ \end{matrix}}\right.}$	Medullary shell simple,			142. Pipetta.
						Medullary shell double,			143. Pipettaria.

Genus 131. Druppula,^[10] n. gen.

Definition.—Druppulida with simple ellipsoidal, cortical shell, and simple medullary shell, without spines or polar tubes.

The genus Druppula, as the simplest form of the Druppulida, may be regarded as the common ancestral form of this subfamily. It may be derived phylogenetically either from Carposphæra by prolongation of one axis, or from Cenellipsis by duplication of the fenestrated shell. The outer (or cortical) shell is always more or less ellipsoidal; the inner (or medullary) shell also is sometimes ellipsoidal, sometimes spherical. Both shells are concentric, connected by a variable number of radial beams. Compare Haliomma oblongum, Harting, 1863, L. N. 18, p. 15, pl. 2, fig. 42.

Subgenus 1. Druppuletta, Haeckel.

Definition.—Pores of the cortical shell regular, hexagonal, or circular.

1. Druppula drupa, n. sp.

Cortical shell thin walled, with smooth surface and regular network; both its axes bear the proportion of 4 : 3. Pores regular, hexagonal, three times as broad as the bars; twelve to fifteen on the half equator. Medullary shell spherical, about one-third as broad as the cortical shell.

Dimensions.—Major axis of the ellipsoidal cortical shell 0.1 to 0.12, minor axis 0.08 to 0.09; pores 0.06, bars 0.02; diameter of the medullary shell 0.03.

Habitat.—Western Tropical Pacific, Station 225, depth 4475 fathoms; also fossil in Barbados.

2. Druppula pandanus, n. sp. (Pl. 39, fig. 3).

Cortical shell thin walled, somewhat rough, with regular network; both its axes bear the proportion of 3 : 2. Pores subregular, circular, hexagonally framed, one and a half times as broad as the elevated bars; ten to twelve on the half equator. Medullary shell spherical, one-fourth as broad as the cortical shell.

Dimensions.—Major axis of the cortical shell 0.16 to 0.17, minor axis 0.11 to 0.12; pores 0.01, bars 0.007; diameter of the medullary shell 0.035.

Habitat.—Pacific, central area, Station 268, depth 2900 fathoms.

3. Druppula cocos, n. sp.

Cortical shell thick walled, somewhat rough, with regular network; proportion of both axes = 6 : 5. Pores regular, circular, hexagonally framed, quite as broad as the elevated bars; fourteen to sixteen on the half equator. Medullary shell ellipsoidal (with longitudinal main axis), nearly half as large as the cortical shell.

Dimensions.—Major axis of the cortical shell 0.07 to 0.08, minor axis 0.6 to 0.65; pores and bars 0.003 to 0.004; diameter of the medullary shell 0.03 and 0.035.

Habitat.—Western Tropical Pacific, Station 222, surface, Indian Ocean, Ceylon, Haeckel.

4. Druppula phœnix, n. sp.

Cortical shell thick walled, smooth, with regular network; proportion of both axes = 5 : 4. Pores regular, circular, hexagonally lobulate (in the same manner as in Stauroxiphus gladius, Pl. 15, fig. 7), three times as broad as the bars; ten to twelve on the half equator. Medullary shell ellipsoidal (with longitudinal main axis), one-third as broad as the cortical shell.

Dimensions.—Major axis of the cortical shell 0.1, minor axis 0.08; pores 0.009, bars 0.003; axis of the medullary shell 0.03 and 0.025.

Habitat.—Mediterranean, Smyrna, Haeckel, surface.

5. Druppula areca, n. sp.

Cortical shell thin walled, with smooth surface and regular network; both its axes bear the proportion of 4 : 3. Pores regular, circular, four times as broad as the bars; fifteen to eighteen on the half equator. Medullary shell spherical, half as broad as the cortical shell.

Dimensions.—Major axis of the ellipsoidal cortical shell 0.12 to 0.14, minor axis 0.1 to 0.11; pores 0.008, bars 0.002; diameter of the medullary shell 0.05 to 0.06.

Habitat.—Indian Ocean, off Bombay, Haeckel.

6. Druppula ovata, Haeckel.

Haliomma ovatum, Ehrenberg, 1854, Mikrogeol., pl. xx. I. fig. 20. Haliomma ovatum, Haeckel, 1862, Monogr. d. Radiol., p. 432.

Cortical shell thin walled, with smooth surface and regular network; proportion of both axes = 3 : 2. Pores regular, circular, three times as broad as the bars; nine to ten on the half equator. Medullary shell spherical, one-third as broad as the cortical shell.

Dimensions.—Major axis 0.08 to 0.1, minor axis 0.05 to 0.06; pores 0.003, bars 0.001; diameter of the medullary shell 0.02.

Habitat.—Fossil in the Tertiary rocks of the Mediterranean coast, Greece (Zante), Ehrenberg; Sicily (Caltanisetta), Haeckel.

7. Druppula caryota, n. sp.

Cortical shell thick walled, with rough surface and regular network; proportion of both axes = 5 : 4. Pores regular, circular, twice as broad as the bars; sixteen to twenty on the half equator. Medullary shell ellipsoidal, one-third as large as the cortical shell.

Dimensions.—Major axis 0.2 to 0.22, minor 0.16 to 0.18, pores 0.008, bars 0.004; axes of the medullary shell 0.07 and 0.055.

Habitat.—Pacific, central area, Stations 266 to 268, depth 2700 to 2900 fathoms.

Subgenus 2. Druppulissa, Haeckel.

Definition.—Pores of the cortical shell irregular, of different form or size, usually subcircular or roundish, sometimes lobed or compound.

8. Druppula nucula, n. sp.

Cortical shell thin walled, smooth, with irregular network; its two axes bear the proportion 3 : 2. Pores subcircular or irregular, roundish, twice to four times as broad as the bars; fifteen to twenty on the half equator. Medullary shell spherical, about one-third as broad as the cortical shell.

Dimensions.—Major axis of the cortical shell 0.15 to 0.2, minor axis 0.1 to 0.14; pores 0.006 to 0.012, bars 0.03; diameter of the medullary shell 0.04.

Habitat.—Cosmopolitan; Mediterranean, Atlantic, Pacific, surface.

9. Druppula elliptica, Haeckel.

Haliomma ellipticum, Stöhr, 1880, Palæontogr., loc. cit., p. 88, Taf. i. fig. 11.

Cortical shell thin walled, rough, or thorny, with irregular network; proportion of the axes = 3 : 2. Pores subcircular or irregular, roundish, about as broad as the bars; ten to twelve on the half equator. Medullary shell half as broad as the cortical shell, irregularly polyhedral (with crooked beams in its interior).

Dimensions.—Major axis 0.15, minor 0.06; pores and bars 0.006; diameter of the medullary shell 0.03.

Habitat.—Fossil in the Tertiary rocks of Sicily: Grotte (Stöhr), Caltanisetta (Haeckel).

10. Druppula prunum, n. sp.

Cortical shell thick walled, smooth, with irregular network; proportion of the axes = 5 : 4. Pores subcircular or irregular, roundish, three to four times as broad as the bars; seven to eight on the half equator; every pore is closed at the bottom by a thin membrane, perforated by four to six irregular pores (like Stylatractus sethoporus, Pl. 17, fig. 3). Medullary shell spherical, one-third as broad as the cortical shell.

Dimensions.—Major axis 0.2, minor axis 0.16; pores 0.03, bars 0.01; small enclosed porules 0.01; diameter of the medullary shell 0.05.

Habitat.—Mediterranean, surface, Portofino near Genoa, Haeckel.

11. Druppula oliva, n. sp.

Cortical shell thick walled, rough, with irregular network; proportion of the axes = 5 : 4. Pores irregular, roundish, three to four times as broad as the bars; lobed or composed of several conjugated porules (as in Lithapium halicapsa, Pl. 14, fig. 8); five to six large pores on the half equator. Medullary shell ellipsoidal, about one-third as broad as the cortical shell.

Dimensions.—Major axis of the cortical shell 0.15, minor 0.12; pores 0.02 to 0.03, bars 0.007; diameter of the medullary shell 0.04.

Habitat.—Mediterranean (Corfu), Canary Islands (Lanzerote), Haeckel.

Genus 132. Druppocarpus,^[11] n. gen.

Definition.—Druppulida with simple ellipsoidal cortical shell and simple medullary shell, with numerous radial spines, without polar tubes.

The genus Druppocarpus differs from Druppula only in the radial spines, which arise between the pores of the cortical shell, and therefore exhibits the same relation to it that Ellipsidium bears to Cenellipsis, or Prunocarpus to Prunulum.

Subgenus 1. Druppocarpetta, Haeckel.

Definition.—Network of the cortical shell regular, with meshes of equal size and similar form.

1. Druppocarpus ananassa, n. sp.

Cortical shell thin walled, with regular, circular, hexagonally framed pores, of about the same breadth as the elevated bars; fourteen to sixteen on the half equator. From each hexagon-corner (between every three pores) arises a short thin radial spine, about as long as two pores, three-sided pyramidal at the base. Proportion of both cortical axes = 4 : 3. Medullary shell spherical, half as broad as the cortical shell. (Greatly resembles Druppula pandanus, Pl. 39, fig. 3, but differs in the larger medullary shell and the spines on the surface.)

Dimensions.—Major axis of the ellipsoidal cortical shell 0.16, minor 0.12; pores and bars 0.006; length of the radial spines 0.02; diameter of the medullary shell 0.06.

Habitat.—South Pacific, Station 289, surface.

2. Druppocarpus castanea, n. sp.

Cortical shell thin walled, with regular circular pores (without hexagonal frames), of about the same breadth as the bars; twelve to fourteen on the half equator. Between every three meshes arise a short conical spine with bristle-like apex, twice to four times as long as one pore. Proportion of both cortical axes = 3 : 2. Medullary shell spherical, one-third as broad as the cortical. (Resembles very closely the spherical Haliomma castanea, Haeckel, figured in my Monograph. pl. xxiv. fig. 4.)

Dimensions.—Major axis 0.15, minor axis 0.1; pores and bars 0.005; length of the radial spines 0.01 to 0.02; medullary shell 0.035.

Habitat.—North Atlantic, surface; Canary Islands, Lanzerote, Haeckel.

Subgenus 2. Druppocarpissa, Haeckel.

Definition.—Network of the cortical shell irregular, with meshes of different size or form.

3. Druppocarpus chamaerops, n. sp.

Cortical shell thin walled, with irregular, roundish, or subcircular pores of very different size, twice to six times as broad as the thin bars; eight to twelve on the half equator. Between them arise numerous thin, bristle-like radial spines, about half as long as the equatorial axis, and equal to the diameter of the spherical medullary shell; pores of the latter subregular, circular, very small. (Resembles Prunocarpus artocarpus, Pl. 39, fig. 5, but differs in the simple spherical medullary shell.)

Dimensions.—Major axis 0.12, minor 0.09; meshes 0.005 to 0.02, bars 0.003; length of the radial spines 0.05; diameter of the medullary shell 0.04.

Habitat.—Mediterranean, in the Strait of Gibraltar, Algesiras, Haeckel, surface.

4. Druppocarpus borassus, n. sp.

Cortical shell thick walled, with irregular, roundish, or subcircular pores, three to five times as broad as the bars; twelve to fifteen on the half equator. Irregularly scattered on the surface about twenty to thirty short conical spines; their length equals their basal breadth and the diameter of the largest pores. Medullary shell ellipsoidal, half as large as the cortical.

Dimensions.—Major axis 0.1, minor 0.08; pores 0.006 to 0.01, bars 0.002; length and thickness of the radial spines 0.01; axes of the medullary shell 0.05 and 0.04.

Habitat.—Pacific, central area, Station 268, depth 2900 fathoms.

5. Druppocarpus corypha, n. sp.

Cortical shell thick walled, with irregular, funnel-like, roundish pores, scarcely as broad as the bars; sixteen to twenty on the half equator. Irregularly scattered on the surface about fifteen to twenty three-sided pyramidal radial spines, half as long as the equatorial axis, and as the diameter of the medullary shell.

Dimensions.—Major axis 0.17, minor 0.14; pores and bars 0.003 to 0.009; length of the radial spines 0.08; diameter of the medullary shell 0.09.

Habitat.—Fossil in the Tertiary rocks of the Nicobars, Haeckel.

Genus 133. Prunulum,^[12] n. gen.

Definition.—Druppulida with simple ellipsoidal cortical shell and double medullary shell; without spines or polar tubes.

The genus Prunulum differs from Druppula in the double (not simple) medullary shell, which is sometimes spherical, sometimes ellipsoidal; it may be derived either from Druppula by duplication of the medullary shell, or from Thecosphæra by prolongation of one axis.

Subgenus 1. Prunuletta, Haeckel.

Definition.—Network of the cortical shell regular, with meshes of equal size and similar form.

1. Prunulum frugulum, n. sp.

Cortical shell thin walled, smooth, with regular, hexagonal pores, three times as broad as the bars; ten to twelve on the half equator. Proportion of the major axis of the ellipsoid to the minor = 4 : 3. Both medullary shells spherical. (Differs from Druppula drupa almost entirely in the double medullary shell.)

Dimensions.—Major axis of the ellipsoidal cortical shell 0.12, minor 0.09; pores 0.006, bars 0.002; diameter of both medullary shells 0.05 and 0.03.

Habitat.—Pacific, central area, Station 266, depth 2750 fathoms.

2. Prunulum cerasum, n. sp.

Cortical shell thick walled, smooth, with circular, hexagonally framed pores, of the same breadth as the bars; sixteen to eighteen on the half equator. Proportion of the two axes of the ellipsoid = 5 : 4. Both medullary shells spherical. (The cortical shell resembles that of Pipetta tuba, Pl. 39, fig. 7, without the polar tubes.)

Dimensions.—Major axis 0.15, minor 0.12; pores and bars 0.007; diameter of the medullary shells 0.08 and 0.04.

Habitat.—South Atlantic, Station 332, depth 2200 fathoms.

3. Prunulum amygdalum, n. sp.

Cortical shell thick walled, smooth, with regular, circular, hexagonally lobulated pores, three times as broad as the bars; twelve to fourteen on the half equator (of the same form as in Druppula phœnix and in Stauroxiphos gladius, Pl. 15, fig. 7). Proportion of the two axes = 6 : 5. Inner medullary shell spherical, outer ellipsoidal.

Dimensions.—Major axis 0.12, minor 0.1; pores 0.009, bars 0.003; diameter of the medullary shells 0.07 and 0.04.

Habitat.—Mediterranean (Corfu), surface.

4. Prunulum coccymelium (Pl. 39, fig. 4).

Cortical shell thin walled, slightly rough, with regular, circular pores, twice as broad as the bars; twelve to fifteen on the half equator. Proportion of both axes = 4 : 3. Both medullary shells spherical.

Dimensions.—Major axis 0.12, minor 0.09; pores 0.006, bars 0.003; diameter of the medullary shells 0.06 and 0.03.

Habitat.—Pacific, central area, Station 273, depth 2350 fathoms.

5. Prunulum crenatum, Haeckel.

? Haliomma crenatum, Ehrenberg, 1854, Mikrogeol., Taf. xxii. fig. 36.

Actinomma crenatum, Stöhr, 1880, Palæontogr., vol. xxvi. p. 94, Taf. iii. fig. 3.

Caryolithis crenata, Ehrenberg, 1847, Monatsber. d. k. preuss. Akad. d. Wiss. Berlin, p. 43.

Cortical shell thick walled, slightly rough or thorny, with small, regular, circular pores, of the same breadth as the bars; sixteen to eighteen on the half equator. Proportion of the two axes = 4 : 3. Both medullary shells ellipsoidal. (The figure of Stöhr represents exactly the fossil form, as I have observed it myself in the Caltanisetta rocks, whilst the figure of Ehrenberg is inaccurate and doubtful. The same form, somewhat variable in size and in the number of the pores, I have also observed in the Pacific ooze.)

Dimensions.—Major axis 0.14 to 0.17, minor 0.1 to 0.13; pores and bars 0.006; main axes of the medullary shells 0.09 and 0.03.

Habitat.—Fossil in the Tertiary rocks of Sicily (Grotte and Caltanisetta); living in the Central Pacific, Station 268, depth 2900 fathoms.

6. Prunulum triplex, Haeckel.

Haliomma triplex, Ehrenberg, 1854, Microgeol., Taf. xxxvB. fig. Biv., q. Actinomma triplex, Haeckel, 1862, Monogr. d. Radiol., p. 444.

Cortical shell thin walled, covered with numerous very thin, short, bristle-like spines. Pores small, regular, circular, of the same breadth as the bars; fourteen to sixteen on the half equator. Proportion of the two axes = 3 : 2. Both medullary shells ellipsoidal. The description of Ehrenberg—as is very often the case—is quite incongruent with his figure. From a combination of both I give here the diagnosis of a deep-sea species, which is possibly identical with it. The velvet-like covering of very short and thin bristles is peculiarly characteristic of this species.

Dimensions.—Major axis 0.1, minor 0.065; pores and bars 0.004; main axes of the medullary shells 0.04 and 0.02.

Habitat.—North Atlantic, 1800 fathoms, Ehrenberg; Station 353, depth 2965 fathoms.

Subgenus 2. Prunulissa, Haeckel.

Definition.—Network of the cortical shell irregular, with meshes of different form or size (usually roundish, but sometimes lobed or compound).

7. Prunulum persicum, n. sp.

Cortical shell thick walled, with smooth surface and irregular, roundish, double-contoured pores, twice to four times as broad as the bars; eight to ten on the half equator. Some of the pores are simple, often subcircular, others lobed, i.e., composed of from two to three confluent pores as in Amphisphæra pluto (Pl. 17, fig. 7). Proportion of the two axes = 3 : 2. Both medullary shells ellipsoidal (or the inner spherical).

Dimensions.—Major axis 0.12, minor 0.08; pores 0.06 to 0.012, bars 0.003; main axes of the medullary shells 0.05 and 0.025.

Habitat.—Indian Ocean, between Socotra and Ceylon, surface, Haeckel.

8. Prunulum fenestratum, Haeckel.

Actinomma fenestratum, Stöhr, 1880, Palæontogr., vol. xxvi. p. 94, Taf. iii. fig. 2.

Cortical shell thick walled, rough, with irregular, roundish pores, once to three times as broad as the bars; twelve to fourteen on the half equator. Proportion of the two axes = 9 : 8. Both medullary shells ellipsoidal. (The pores in Stöhr's description are by mistake called "regular"; in the figure they are very irregular, as also in the fossil specimens observed by myself. Between the cortical pores arise very short irregular thorns.)

Dimensions.—Major axis 0.12 to 0.15, minor 0.1 to 0.12; pores 0.003 to 0.01, bars 0.003; main axis of the outer medullary shell 0.07 to 0.09, of the inner 0.03 to 0.04.

Habitat.—Fossil in the Tertiary rocks of Sicily; Grotte, Stöhr, Caltanisetta, Haeckel.

9. Prunulum pyrenium, n. sp.

Cortical shell very thick walled, smooth, with large irregular, roundish pores, three to four times as broad as the bars; six to eight on the half equator. The bottom of each funnel-like pore is closed by a thin siliceous membrane, perforated by three to five irregular roundish pores. Proportion of the two axes = 4 : 3. Both medullary shells ellipsoidal. (Closely resembles Stylatractus sethoporus, Pl. 17, figs. 2, 3, but is devoid of the polar spines.)

Dimensions.—Major axis 0.16, minor 0.12; pores 0.015 to 0.02, bars 0.005; porules 0.01; main axes of the medullary shells 0.07 and 0.03.

Habitat.—Western Tropical Pacific, Station 225, depth 4475 fathoms.

Genus 134. Prunocarpus,^[13] n. gen.

Definition.—Druppulida with simple ellipsoidal cortical shell and double medullary shell, with numerous radial spines, but without polar tubes.

The genus Prunocarpus differs from Prunulum only in the radial spines of the cortical shell, and exhibits therefore the same relation to it that Druppocarpus bears to Druppula. While in the latter the medullary shell is simple, in the former it is double.

Subgenus 1. Prunocarpetta, Haeckel.

Definition.—Network of the cortical shell regular, with meshes of equal size and similar form.

1. Prunocarpus datura, n. sp.

Cortical shell thick walled, with regular, circular pores, twice as broad as the bars; ten to twelve on the half equator. Between every three meshes arises a short conical spine, twice to three times as long as one pore. Both medullary shells spherical. (Differs mainly from Ellipsidium datura and from Druppocarpus castanea in the double medullary shell. The outer network resembles Haliomma castanea, figured 1862 in my Monograph, Taf. xxiv. fig. 4.)

Dimensions.—Major axis of the ellipsoid 0.16, minor 0.12; pores 0.012, bars 0.006; length of the radial spines 0.03; diameter of the medullary shells 0.06 and 0.04.

Habitat.—North Atlantic, Færöe Channel, John Murray, surface.

2. Prunocarpus sparganium, n. sp.

Cortical shell thick walled, with very small, numerous, regular, circular pores, of the same size as the bars; forty to fifty on the half equator. Between them over the entire surface occur small conical spines. Irregularly scattered over the surface ten to twenty larger conical spines, three to six times as thick at the base as one pore, one-fourth to one-half as long as the main axis. Both medullary shells ellipsoidal.

Dimensions.—Major axis of the cortical shell 0.16, of the outer medullary shell 0.11, of the inner 0.06; equatorial axis of the first shell 0.12, of the second 0.08, of the third 0.04; pores and bars on an average 0.005; length of the spines 0.05 to 0.1, basal breadth 0.02 to 0.03.

Habitat.—Fossil in the Barbados deposits (Haeckel).

Subgenus 2. Prunocarpilla, Haeckel.

Definition.—Network of the cortical shell irregular, with meshes of different size or form.

3. Prunocarpus artocarpium, n. sp. (Pl. 39, fig. 5).

Cortical shell thin walled with irregular, roundish pores of very different sizes, twice to nine times as broad as the thin bars; ten to fifteen on the half equator. Between them arise numerous bristle-shaped, radial spines, with conical base, on an average one-fourth to two-thirds as long as the equatorial axis. The outer medullary shell, with irregular, roundish pores, presents a transverse ellipsoid, its main axis lying in the equatorial axis of the cortical shell, whilst its equatorial axis corresponds to the main axis of the latter. Inner medullary shell very small, spherical, with very small pores.

Dimensions.—Major axis of the cortical shell 0.14, of the outer medullary shell 0.05; minor axis of the former 0.1, of the latter 0.035; diameter of the inner medullary shell 0.014; pores of the cortical shell 0.005 to 0.02, bars 0.002; length of the radial spines 0.02 to 0.06.

Habitat.—Indian Ocean, surface; Ceylon, Belligemma, Haeckel.

4. Prunocarpus melocactus, n. sp.

Cortical shell thick walled, with irregular, roundish pores, twice to five times as broad as the bars; eighteen to twenty-four on the half equator. Between them arise over the entire surface small conical thorns, not longer than the largest pores. Irregularly scattered over the surface twenty to thirty strong, conical, radial spines, about half as long as the main axis, as broad at the base as a large pore. Both medullary shells ellipsoidal, their main axis identical with that of the cortical shell.

Dimensions.—Major axis of the outer shell 0.18, of the middle 0.09, of the inner 0.05; minor axis of the first 0.14, of the second 0.07, of the third 0.04; pores of the cortical shell 0.006 to 0.02, bars 0.004; length of the spines 0.1, basal breadth 0.01.

Habitat.—Pacific, central area, Station 268, depth 2900 fathoms; also fossil in the Tertiary rocks of Sicily; Caltanisetta, Haeckel.

Genus 135. Cromyodruppa,^[14] n. gen.

Definition.—Druppulida with four or more concentric shells (two medullary and two or more cortical shells), without spines or polar tubes.

The genus Cromyodruppa is characterised by the multiplication of the concentric fenestrated shell, which is composed of two medullary shells (enclosed in the central capsule) and two or more cortical shells (outside it). The former may be either spherical or ellipsoidal. The latter are always ellipsoidal, and in this it differs from Cromyosphæra. Probably Cromyodruppa has arisen from Prunulum by secondary apposition of more cortical envelopes.

Subgenus 1. Cromyodruppium, Haeckel.

Definition.—Shell composed of four concentric shells, two medullary and two cortical.

1. Cromyodruppa cepa, n. sp.

Shell composed of two ellipsoidal, cortical, and two spherical medullary shells. Proportion of the main axes of the four shells = 1 : 2 : 4 : 5. Network of all four shells nearly of the same form, subregular, with circular pores of almost equal size in every shell. The absolute size of the pores increases from the innermost to the outermost shell, but the breadth of the bars does not increase in a similar degree. The bars of the outermost shell are only twice as broad as those of the innermost; but the pores are three to four times larger. Surface of all four shells smooth. (The shell greatly resembles that of Cromyatractus tetraphractus, Pl. 15, fig. 2, but is devoid of polar spines; it differs also in the spherical form of both medullary shells and their relative size.)

Dimensions.—Main axes of the four shells—(A) innermost 0.035, (B) second 0.08, (C) third 0.15, (D) outermost 0.2; their equatorial axes—(A) 0.03, (B) 0.08, (C) 0.12, (D) 0.16; pores 0.004 to 0.016, bars 0.002 to 0.004.

Habitat.—Western Tropical Pacific, Station 198, depth 2150 fathoms.

Subgenus 2. Caryodruppula, Haeckel.

Definition.—Shell composed of five or more concentric shells (two medullary and three or more cortical).

2. Cromyodruppa mango, n. sp.

Shell composed of six ellipsoidal, concentric shells, two medullary and four cortical. Proportion of their main axes = 2 : 3 : 8 : 11 : 14 : 18. Network of the two medullary shells and of the innermost cortical shell subregular, with subcircular pores, about the same breadth as the bars. Network of the three outer cortical shells more lax, with larger, irregular, roundish pores, twice to six times as broad as the bars. The size of the pores and bars increases gradually from the innermost to the outermost shell. Surface smooth.

Dimensions.—Main axis of the six shells—(A) innermost 0.04, (B) 0.06, (C) 0.16, (D) 0.22, (E) 0.28, (F) 0.35; their equatorial axes—(A) innermost 0.03, (B) 0.05, (C) 0.12, (D) 0.16, (E) 0.2, (F) 0.25; pores 0.003 to 0.02, bars 0.003 to 0.005.

Habitat.—Indian Ocean, surface; Matura, Ceylon, Haeckel.

Genus 136. Cromyocarpus,^[15] n. gen.

Definition.—Druppulida with four or more concentric shells (two medullary and two or more cortical shells), with numerous radial spines, but without polar tubes.

The genus Cromyocarpus differs from Cromyodruppa only in the development of numerous large radial spines which start from the outer surface of the shell. It exhibits therefore the same relation to the latter that Prunocarpus bears to Prunulum, or Druppocarpus to Druppula. It differs from both in the multiplication of the cortical shell.

1. Cromyocarpus quadrifarius, n. sp.

Shell composed of four concentric shells, two ellipsoidal cortical shells, and two spherical medullary shells. Proportion of their main axes = 10 : 8 : 3 : 2. Pores of the two cortical shells irregular, roundish, twice to four times as broad as the bars. Pores of the two medullary shells subregular, circular, about the same size as the bars. Outer surface covered with numerous conical radial spines, about half as long as the main axis, half as broad at the base as the innermost shell.

Dimensions.—Major axis of the outer cortical shell 0.2, of the inner 0.15; equatorial axis of the former 0.16, of the latter 0.12; diameter of the outer medullary shell 0.06, of the inner 0.04; pores of the cortical shells 0.01 to 0.02, of the medullary shells 0.004 to 0.008, bars 0.003 to 0.006; length of the radial spines 0.1, basal breadth 0.02.

Habitat.—Indian Antarctic Ocean, Station 157, depth 1950 fathoms.

Genus 137. Lithatractus,^[16] n. gen.

Definition.—Druppulida with simple ellipsoidal cortical shell and simple medullary shell, with two large opposite polar spines in the main axis of equal size and similar form.

The genus Lithatractus, rich in common and widely distributed species, begins the series of those Druppulida which are characterised by peculiar polar spines at both poles of the main axis. It repeats the formation of Stylosphæra and Ellipsostylus, and differs from the former in the ellipsoidal form of the cortical shell, from the latter in the possession of a medullary shell. Formerly all these forms were united in the one genus Stylosphæra (see above, p. 121).

Subgenus 1. Lithatractara, Haeckel.

Definition.—Network of the outer shell regular or subregular, with meshes of nearly equal size and similar form; surface smooth, without thorns or papillæ.

1. Lithatractus hexagonalis, n. sp.

Outer shell thin walled, smooth, without thorns or papillæ, with regular delicate network; the meshes hexagonal, three to four times as broad as the thin bars; ten to twelve on the half equator. Proportion of the major axis of the ellipsoid to the minor = 4 : 3. Minor axis three times as large as that of the inner spherical shell; pores of the latter, small, circular. Two spines three-sided pyramidal, as long as the radius of the outer shell, each as broad at its base as one mesh.

Dimensions.—Longer axis of the ellipsoidal cortical shell 0.16, shorter axis 0.12; pores 0.011, bars 0.003; diameter of the spherical medullary shell 0.04; length of the polar spines 0.07; basal breadth 0.01.

Habitat.—North Pacific, Station 253, depth 3125 fathoms.

2. Lithatractus fragilis, n. sp. (Pl. 16, fig. 3).

Stylosphæra fragilis, Haeckel, 1881, Prodromus et Atlas, pl. xvi. fig. 3.

Outer shell thin walled, smooth, without thorns or papillæ, with regular network; the meshes circular, of equal size, eight to ten times as broad as the thin bars; six to eight on the half equator. Proportion of the major axis of the ellipsoid to the minor = 5 : 4. Minor axis once and one-third as broad as that of the ellipsoidal inner shell, the pores of which are also circular, but of half the size. Two spines strong, three-sided pyramidal, acute, as broad as a large mesh, as long as the equatorial axis. The stout inner prolongations of these form the only connection between the two shells.

Dimensions.—Longer axis of the ellipsoidal cortical shell 0.12, shorter axis 0.1; pores 0.02, bars 0.002; longer axes of the ellipsoidal medullary shell 0.09, shorter axis 0.07; pores 0.01, bars 0.002; length of the polar spines 0.1, basal breadth 0.002.

Habitat.—Central area of the Pacific, Station 272, depth 2600 fathoms.

3. Lithatractus leptostylus, n. sp.

Outer shell thin walled, smooth, with regular, circular pores of equal size, three to four times as broad as the thin bars; ten to twelve on the half equator. Proportion of the major axis to the minor = 7 : 6. Minor axis three times as large as that of the inner spherical shell; pores of the latter half as large. Polar spines cylindrical, blunt, longer than the major axis, scarcely half as broad as one larger pore.

Dimensions.—Longer axis of the cortical shell 0.14, shorter axis 0.12; pores 0.015 to 0.02, bars 0.004; diameter of the medullary shell 0.04; length of the polar spines 0.15 to 0.2, its thickness 0.01.

Habitat.—Central area of the Pacific, Stations 270 to 272, depth 2425 to 2925 fathoms.

4. Lithatractus pachystylus, n. sp.

Outer shell thick walled, smooth, with regular, circular pores of equal size; twelve to fifteen on the half equator. Each pore is deep, funnel-shaped, its outer aperture double the size of the inner, its breadth about three times that of the high bars. Proportion of the major axis to the minor = 6 : 5. Major axis double as long as the diameter of the spherical medullary shell. Polar spines very thick and short, tetrahedral, one-fourth as long and broad as the major axis.

Dimensions.—Longer axis of the cortical shell 0.17, shorter axis 0.14; pores 0.01, bars 0.003; diameter of the medullary shell 0.08; length and thickness of the polar spines 0.04.

Habitat.—Central area of the Pacific, Station 271, depth 2425 fathoms.

5. Lithatractus convallaria, n. sp.

Outer shell thick walled, smooth, with elegant regular network; the meshes circular, six-lobed, rosette-like (of the same form as Stauroxiphos gladius, Pl. 15, fig. 7), twice to three times as broad as the bars; six to eight on the half equator. Proportion of the major axis of the ellipsoid to the minor = 4 : 3. Minor axis twice as long as the diameter of the inner spherical shell, which has regular, simple, circular pores of half the size. Polar spines short and thick, conical, only one-fourth to one-sixth as long as the minor axis, and quite as thick.

Dimensions.—Longer axis of the cortical shell 0.16, shorter axis 0.12; pores 0.016, bars 0.006; diameter of the medullary shell 0.06; length of the polar spines 0.02 to 0.03, basal thickness the same.

Habitat.—Central area of the Pacific, Station 268, depth 2900 fathoms.

Subgenus 2. Lithatractylis, Haeckel.

Definition.—Network of the outer shell regular, with meshes of equal size and similar form; surface thorny or papillose, covered with small conical spines or tubercles.

6. Lithatractus echiniscus, n. sp.

Outer shell thorny, thin walled, with regular network; meshes circular, with hexagonal frame, four to five times as broad as the thin bars; eighteen to twenty on the half equator. From every corner between the three meshes, where three hexagons unite, starts one short, straight, triangular thorn (as in Ellipsoxiphus elegans, Pl. 14, fig. 7). Proportion of the major axis of the ellipsoid to the minor = 4 : 3. Minor axis twice the diameter of the inner spherical shell, the pores of which are half as broad, circular. Polar spines three-sided pyramidal, about as long as the minor axis, as broad at the base as one hexagonal frame.

Dimensions.—Longer axis of the cortical shell 0.08, shorter axis = 0.06; pores 0.004, bars 0.001; length of the polar spines 0.05, basal thickness 0.005; diameter of the inner shell 0.03.

Habitat.—South Atlantic, off Tristan da Cunha, Station 334, surface.

7. Lithatractus carduelis, n. sp.

Outer shell thin walled, thorny, with regular network; meshes circular, simple, four to six times as broad as the thin bars; ten to twelve on the half equator. Between every three meshes is one short conical spine. Proportion of the major axis to the minor = 6 : 5. Minor axis equals three times the diameter of the inner spherical shell. Polar spines conical, thick, half as long as the major axis, thicker at the base than one pore. (This species differs from Stylatractus carduus only by the simple medullary shell.)

Dimensions.—Longer axis of the ellipsoid 0.12 to 0.16, shorter axis 0.1 to 0.14; pores 0.02 to 0.03, bars 0.005; length of the polar spines 0.05 to 0.10, basal breadth 0.04; diameter of the medullary shell 0.03 to 0.04.

Habitat.—Central area of the Pacific, Stations 268 to 274, depth 2350 to 2900 fathoms; also fossil in the rocks of Barbados.

8. Lithatractus cirsium, n. sp.

Outer shell thin walled, thorny, with regular network; pores circular, simple, small, two to three times as broad as the thin bars; eighteen to twenty-four on the half equator. Proportion of the major axis to the minor = 4 : 3. Inner shell ellipsoidal, half as large as the outer. Polar spines cylindrical, blunt, thin, very variable in length (one-fourth to three-fourths of the major axis, not thicker than a mesh).

Dimensions.—Longer axis of the ellipsoid 0.07 to 0.09, shorter axis 0.05 to 0.07; pores 0.005 to 0.006, bars 0.002; length of the polar spines 0.02 to 0.06, basal breadth 0.004; length of the inner shell 0.04, breadth 0.03.

Habitat.—North Pacific, Station 244, surface.

9. Lithatractus rosetta, n. sp.

Outer shell thick walled, thorny, with regular network; meshes circular, funnel-shaped, its outer aperture elegant, rosette-like, with eight to ten incisions (like Stylosphæra calliope, Pl. 16, fig. 6); eight to ten meshes on the half equator, three to four times as broad as the bars. Proportion of the longer axis to the shorter = 5 : 4. Shorter axis equals three times the diameter of the inner spherical shell. Polar spines three-sided pyramidal, about half as long as the shorter axis, as broad at the base as a mesh.

Dimensions.—Longer axis of the cortical shell 0.15, shorter 0.12; pores 0.02, bars 0.005; length of the polar spines 0.05, basal breadth 0.02; diameter of the inner shell 0.04.

Habitat.—South-eastern part of the Pacific, Station 302, depth 1450 fathoms.

Subgenus 3. Lithatractona, Haeckel.

Definition.—Network of the outer shell irregular, with meshes of unequal size or dissimilar form; surface smooth, without thorns or papillæ.

10. Lithatractus conifer, n. sp.

Outer shell thin walled, smooth, with irregular, roundish pores, two to four times as broad as the thin bars; fifteen to twenty on the half equator. Margin of the pores simple. Proportion of the major axis to the minor = 3 : 2. Minor axis twice as large as the diameter of the inner spherical shell, the pores of which are also irregular, roundish, but of half the size. Polar spines conical, somewhat shorter than the main axis, on the base two to three times as thick as a large pore.

Dimensions.—Longer axis of the outer shell 0.15, shorter axis 0.1; pores 0.002 to 0.004, bars 0.001; diameter of the inner shell 0.05; length of the polar spines 0.12, basal breadth 0.012.

Habitat.—South Atlantic, Station 325, surface.

11. Lithatractus lobatus, n. sp.

Outer shell thick walled, smooth, with irregular, roundish pores, four to eight times as broad as the bars; six to eight on the half equator. Margin of the pores lobed, very irregular, bluntly dentate, by five to twenty slight incisions. Proportion of the major axis to the minor very variable, between 3 : 2 and 9 : 8. Diameter of the inner shell also variable, between one-third and one-half of the outer; pores of the former scarcely half the size of the latter, simple, roundish, or circular. The inner shell is at some parts quite spherical, at other parts more or less ellipsoidal. Polar spines conical, very variable in size and form, sometimes in the basal half triangular; they are sometimes somewhat longer than the main axis, at other times considerably shorter; their basal breadth is occasionally the same as that of the largest pores, sometimes, however, scarcely half as large. This deep-sea species is very common in the central area of the Tropical Pacific (Stations 266 to 272), and occurs also fossil in the Barbados deposits. It is interesting from its great variability, and sometimes constitutes a transitional form to Stylosphæra.

Dimensions.—Longer axis of the outer shell 0.1 to 0.15, shorter axis 0.05 to 0.12; pores 0.018 to 0.024, bars 0.002 to 0.004; diameter of the inner shell 0.04 to 0.08; length of the polar spines 0.08 to 0.2, basal thickness 0.01 to 0.02.

Habitat.—Central area of the Pacific, common; Stations 266 to 272, depth 2425 to 2900 fathoms; also fossil in Barbados.

12. Lithatractus jugatus, n. sp. (Pl. 16, fig. 2).

Stylosphæra jugata, Haeckel, 1881, Prodromus et Atlas (pl. xvi. fig. 2).

Outer shell thick walled, smooth, or somewhat reticulated, with a peculiar, irregular, double network. The pores are roundish, of very different sizes, with double margin of the outer aperture, and so irregularly distributed in polygonal groups that every group contains two to six pores immediately touching each other; the groups are separated by broader bars. On the half equator of the shell are about six to eight groups and twelve to eighteen pores. Proportion of the longer axis of the ellipsoidal shell to the shorter = 6 : 5 or 5 : 4. Inner ellipsoidal shell about half the size; its pores are not easy to make out. Polar spines three-sided pyramidal, with prominent edges, about half as long as the major axis, as broad at the base as a group of pores. (Nearly allied to Stylosphæra jugata, p. 137.)

Dimensions.—Longer axis of the cortical shell 0.12 to 0.16, shorter axis 0.1 to 0.13; pores 0.01 to 0.02; length of the polar spines 0.06 to 0.08, basal breadth 0.03 to 0.4.

Habitat.—Central area of the Pacific, Stations 266 to 272, depth 2425 to 2900 fathoms.

Subgenus 4. Lithatractium, Haeckel.

Definition.—Network of the outer shell irregular, with meshes of unequal size or dissimilar form; surface thorny or papillose, covered with small conical spines or tubercles.

13. Lithatractus conostylus, n. sp.

Outer shell thorny, thin walled, with irregular network; pores roundish, of unequal size, twice to four times as broad as the thin bars; sixteen to twenty on the half equator. Proportion of the longer axis to the shorter = 5 : 4. Shorter axis twice the diameter of the inner spherical shell. Polar spines conical, very stout, longer than the main axis, its base equals one-third of the minor axis.

Dimensions.—Major axis of the cortical shell 0.1, shorter axis 0.08; pores 0.004 to 0.002, bars 0.001; diameter of the medullary shell 0.04; polar spines—length 0.12, thickness 0.03.

Habitat.—Central area of the Pacific, Station 271, depth 2425 fathoms.

14. Lithatractus gamoporus, n. sp.

Outer shell thorny, thick walled, with irregular network; pores roundish, of unequal size, so irregularly distributed in polygonal groups that in every group two to six pores (commonly three to four) are near together; the groups are separated by broader bars. On the half equator six to eight groups and eighteen to twenty-four pores. Proportion of the longer axis to the shorter = 6 : 5. Shorter axis equals twice the diameter of the inner ellipsoidal shell. Polar spines three-sided pyramidal, about as long as the equatorial axis, as broad at the base as a group of pores.

Dimensions.—Major axis of the cortical shell 0.12, minor axis 0.1; pores 0.004 to 0.012, bars 0.003; length of the polar spines 0.1, basal breadth 0.03.

Habitat.—Central area of the Pacific, Stations 271 to 274, depth 2350 to 2750 fathoms.

Genus 138. Druppatractus,^[17] n. gen.

Definition.—Druppulida with simple ellipsoidal cortical shell and simple medullary shell, with two large opposite polar spines in the main axis of different size or dissimilar form.

The genus Druppatractus differs from its near relation Lithatractus in the differentiation of the two polar spines, which are different in size or form, often to a very considerable degree. It has therefore the same relation to the latter that Ellipsoxiphus bears to Ellipsostylus.

Subgenus 1. Druppatractara, Haeckel.

Definition.—Network of the cortical shell regular or subregular, with meshes of nearly equal size and similar form; surface smooth, without thorns or papillæ.

1. Druppatractus ichthydium, n. sp.

Cortical shell thin walled, with smooth surface and regular network. Proportion of the major axis to the minor = 3 : 2. Pores circular, hexagonally framed, twice as broad as the bars; seven to eight on the half equator (as in Xiphostylus alcedo, Pl. 13, fig. 4). Medullary shell spherical, one-third as broad as the cortical shell. Polar spines straight, three-sided pyramidal, as broad at the base as one mesh; the longer equals the main axis of the cortical shell, the shorter only its half.

Dimensions.—Major axis of the ellipsoidal cortical shell 0.18, minor axis 0.12; pores 0.01, bars 0.005; diameter of the medullary shell 0.04; length of the major polar spine 0.16 to 0.2, of the minor 0.01 to 0.12, basal breadth 0.01.

Habitat.—Mediterranean (Corfu), surface, Haeckel.

2. Druppatractus hippocampus, n. sp. (Pl. 16, figs. 10, 11).

Stylosphæra hippocampus, Haeckel, 1881, Atlas, pl. xvi. figs. 10, 11.

Cortical shell thick walled, with smooth surface and regular network. Proportion of both axes = 7 : 6. Pores circular, hexagonally lobed, three times as broad as the bars; nine to ten on the half equator. Medullary shell ellipsoidal, nearly half as large as the cortical. Larger polar spine horn-like curved, as long as the main axis, smaller scarcely half as long, pommel-shaped.

Dimensions.—Major axis 0.09, minor 0.075; pores 0.01, bars 0.003; axes of the medullary shell 0.04 and 0.03; length of the larger polar spine 0.06 to 0.09, of the smaller 0.04, basal breadth 0.02.

Habitat.—Pacific, central area, Stations 270 to 272, surface.

3. Druppatractus belone, n. sp.

Cortical shell thin walled, with smooth surface and regular network. Proportion of both axes = 4 : 3. Pores circular, twice as broad as the bars; ten to twelve on the half equator. Medullary shell spherical, one-third as broad as the cortical shell. Polar spines strong, straight, cylindrical, with conical apex, as broad at the base as two pores; the larger once and a half to twice as long as the main axis, the smaller only one-third to one-fourth as long.

Dimensions.—Major axis 0.1 to 0.12, minor 0.08 to 0.09; pores 0.008, bars 0.004; diameter of the medullary shell 0.03; length of the larger polar spine 0.15 to 0.2, of the minor 0.04 to 0.05, basal thickness of them 0.02.

Habitat.—Cosmopolitan; Atlantic, Indian, and Pacific, surface.

4. Druppatractus testudo, Haeckel.

Stylosphæra testudo, Ehrenberg, 1872, Abhandl. d. k. Akad. d. Wiss. Berlin, p. 299, Taf. viii. fig. 16.

Cortical shell thick walled, spindle-shaped, with smooth surface and regular network. Proportion of the two axes = 3 : 2. Pores circular, five times as broad as the bars; only six to seven on the half equator. Medullary shell ellipsoidal, about one-third as large as the cortical shell. Polar spines strong, short, three-sided pyramidal; the larger as long as half the transverse axis, the smaller only one-fourth as long.

Dimensions.—Major axis 0.12, minor 0.8; pores 0.015, bars 0.003; axes of the medullary shell 0.04 and 0.03; length of the larger polar spine 0.04, of the smaller 0.02, basal thickness 0.01.

Habitat.—Pacific, Philippine and Californian Sea (Ehrenberg), Stations 244, 266, 289, &c., depth 2550 to 2900 fathoms.

Subgenus 2. Druppatractylis, Haeckel.

Definition.—Network of the cortical shell regular or subregular, with meshes of nearly equal size and similar form; surface thorny or papillose, covered with small conical spines or tubercles.

5. Druppatractus accipenser, n. sp.

Cortical shell thick walled, thorny, with regular network. Proportion of the two axes = 6 : 5. Pores circular, each with a six-lobed outer opening, funnel-shaped, twice as broad as the bars; nine to ten on the half equator. Medullary shell spherical, one-third as broad as the cortical shell. Polar spines very strong, three-sided pyramidal, as broad at the base as three pores; the larger about as long as the main axis, the smaller only one-third as long.

Dimensions.—Major axis 0.12, minor 0.1; pores 0.01, bars 0.005; medullary shell 0.035; length of the larger polar spine 0.11, of the smaller 0.04, basal breadth 0.03.

Habitat.—Indian Ocean, Madagascar, surface, Rabbe.

6. Druppatractus ostracion, n. sp. (Pl. 16, figs. 8, 9).

Cortical shell thick walled, thorny, with regular network. Proportion of the two axes = 4 : 3. Pores circular, hexagonally framed, three to four times as broad as the crested bars; from every corner of the hexagon (between three meshes) arises a short papilla; the bottom of every funnel-like mesh is closed by a very thin plate with three regular, circular pores (occasionally four), sometimes confluent, at other times separate. Medullary shell (fig. 9) half as large as the cortical, ellipsoidal and papillate, with regular, circular pores. Polar spines very strong, three-sided prismatic, often somewhat irregular, with short apex; the larger once to twice as long as the main axis, the smaller scarcely half as long.

Dimensions.—Major axis 0.16, minor 0.12; pores 0.02 (porules at their base 0.01), bars 0.006; axes of the medullary shell 0.07 and 0.06, its pores 0.01, bars 0.003; length of the larger polar spine 0.15 to 0.3, of the smaller 0.07 to 0.09, basal thickness 0.03.

Habitat.—Pacific, central area, Station 265, depth 2900 fathoms.

7. Druppatractus coronatus, Haeckel.

Stylosphæra coronata, Ehrenberg, 1875, Abhandl. d. k. Akad. d. Wiss. Berlin, p. 84, Taf. xxv. fig. 4.

Cortical shell thick walled, thorny, with regular network. Proportion of the two axes = 5 : 4. Pores circular, simple, twice as broad as the bars; eight to ten on the half equator. Medullary shell circular, one-third as broad as the cortical shell. Polar spines furrowed and angular; the longer and thinner pyramidal about as long as the main axis, the shorter and thicker scarcely half as long, thickened towards the short conical apex.

Dimensions.—Major axis 0.08 to 0.1, minor 0.06 to 0.08; pores 0.01, bars 0.005; diameter of the medullary shell 0.03; length of the large polar spine 0.08 to 0.12, of the shorter 0.04 to 0.05.

Habitat.—Fossil in the Tertiary rocks of Barbados; also living in the depths of the Pacific, central area, Stations 265 to 268, depth 2700 to 2900 fathoms.

Subgenus 3. Druppatractona, Haeckel.

Definition.—Network of the cortical shell irregular, with meshes of unequal size or dissimilar form; surface smooth, without thorns or papillæ.

8. Druppatractus lævis, Haeckel.

Stylosphæra lævis, Ehrenberg, 1875, Abhandl. d. k. Akad. d. Wiss. Berlin, p. 84, Taf. xxv. fig. 6.

Cortical shell thin walled, smooth, with irregular network. Proportion of the two axes = 3 : 2. Pores roundish or subcircular, of different size, one-half to twice as broad as the bars; eight to ten on the half equator. Medullary shell ellipsoidal, one-third as large as the cortical shell. Polar spines conical, the larger and thinner nearly as long as the main axis, the shorter and thicker scarcely one-third as long.

Dimensions.—Major axis 0.07 to 0.1, minor 0.05 to 0.07; pores and bars 0.005 to 0.01; axes of the medullary shell 0.03 and 0.02; length of the major polar spine 0.06 to 0.09, of the shorter 0.03 to 0.04.

Habitat.—Cosmopolitan; Atlantic, Indian, Pacific, surface.

9. Druppatractus xiphias, n. sp.

Cortical shell thick walled, smooth, with irregular network. Proportion of the two axes = 6 : 5. Pores funnel-shaped, composed of two to four confluent smaller porules, twice to four times as broad as the bars; ten to twelve on the half equator. Medullary shell spherical, half as broad. Polar spines three-sided pyramidal, the larger about as long as the main axis, the shorter one-third to one-half as long.

Dimensions.—Major axis 0.12, minor 0.1; pores 0.012 to 0.018, bars 0.004; diameter of the medullary shell 0.05; length of the major polar spine 0.1, of the minor 0.03 to 0.05.

Habitat.—Pacific, central area, Station 268, depth 2900 fathoms.

Subgenus 4. Druppatractium, Haeckel.

Definition.—Network of the cortical shell irregular, with meshes of unequal size or dissimilar form; surface thorny or papillose, covered with small spines or tubercles.

10. Druppatractus diodon, n. sp.

Cortical shell thin walled, thorny, with irregular network. Proportion of the two axes = 5 : 4. Pores simple, irregular, roundish, twice to four times as broad as the bars; eight to ten on the half equator. Medullary shell spherical, half as broad. Polar spines conical, more or less curved; the major longer than the main axis, the minor scarcely half as long. (Resembles Sphærostylus ophidium, Pl. 16, figs. 14, 15, but differs from it in the prolongation of the main axis.)

Dimensions.—Major axis 0.15, minor 0.12; pores 0.01 to 0.02, bars 0.005; diameter of the medullary shell 0.06; length of the larger polar spine 0.12 to 0.18, of the shorter 0.06 to 0.08, basal thickness 0.003.

Habitat.—Pacific, central area, Station 274, surface.

11. Druppatractus pisciculus, n. sp.

Cortical shell thick walled, spiny, with irregular network. Proportion of the two axes = 3 : 2. Pores irregular, roundish, lobed, or composed of three to five confluent porules, twice to six times as broad as the bars; six to eight on the half equator. (Similar to Ellipsoxiphus atractus, Pl. 14, fig. 1.) Medullary shell ellipsoidal, nearly half as large as the cortical shell. Polar spines three-sided pyramidal, the major longer than the main axis, the minor scarcely one-third to one-fourth as long.

Dimensions.—Major axis 0.18, minor 0.12; pores 0.01 to 0.03, bars 0.004; axes of the medullary shell 0.08 and 0.05; length of the major polar spine 0.2, of the minor 0.05, basal breadth 0.02.

Habitat.—South Atlantic, Station 332, depth 2200 fathoms.

Genus 139. Stylatractus,^[18] n. gen.

Definition.—Druppulida with simple ellipsoidal cortical shell and double medullary shell, in the main axis with two large opposite polar spines of equal size and similar form.

The genus Stylatractus differs from Lithatractus in the double medullary shell, from Amphisphæra in the ellipsoidal form of the cortical shell. As in these two genera, both opposite polar spines have the same shape and size.

Subgenus 1. Stylatractara, Haeckel.

Definition.—Network of the cortical shell regular or subregular, with meshes of nearly equal size and similar form; surface smooth, without thorns or papillæ.

1. Stylatractus neptunus, n. sp. (Pl. 17, fig. 6).

Amphistylus neptunus, Haeckel, 1878, Atlas, pl. xvii. fig. 6.

Cortical shell thick walled, smooth, with subregular, circular, polygonally framed pores, quite as broad as the bars; ten to twelve on the half equator. Polar spines three-sided pyramidal, about as long as the half main axis, three times as broad at the base as the pores. (Much resembles Amphisphæra neptunus, p. 142, but differs from it by the prolongation of the main axis, which equals one and a half or one and a fourth the equatorial axis, and by the somewhat irregular formation of the cortical hexagonal network. Sometimes also, as in the figured specimen, the length of both polar spines is somewhat different.)

Dimensions.—Major axis of the cortical shell 0.15, minor axis 0.12; pores and bars 0.007; main axes of both ellipsoidal medullary shells 0.08 and 0.05; length of the polar spines 0.08 to 0.1, basal breadth 0.02.

Habitat.—Pacific, central area, Stations 266 to 268, depth 2700 to 2900 fathoms.

2. Stylatractus fusiformis, n. sp.

Cortical shell thick walled, smooth, with regular, simple, circular pores, quite as broad as the bars; fourteen to sixteen on the half equator. Polar spines three-sided pyramidal, half as long as the main axis, as broad at the base as the inner medullary shell. (Resembles very nearly Xiphatractus armadillo, Pl. 17, fig. 11, but differs in the regular form and equal length of the polar spines.)

Dimensions.—Major axis 0.17, minor axis 0.13; pores and bars 0.007; main axes of both ellipsoidal medullary shells 0.09 and 0.05; length of the polar spines 0.08, basal breadth 0.04.

Habitat.—Cosmopolitan; Atlantic, Indian, Pacific, at various depths.

3. Stylatractus compactus, n. sp. (Pl. 17, fig. 4).

Cortical shell thick walled, smooth, with subregular, circular, double-contoured pores, smaller than the bars; sixteen to eighteen on the half equator. The thickness of the shell-wall equals the radius of the inner medullary shell. Polar spines short, three-sided pyramidal; their length and basal thickness variable, but commonly equal to the diameter of the inner medullary shell.

Dimensions.—Major axis 0.16, minor axis 0.13; pores 0.007, bars 0.01; main axes of both ellipsoidal medullary shells 0.09 and 0.04; length and basal breadth of the polar spines 0.04 to 0.05.

Habitat.—Pacific, central area, Stations 270 to 272, depth 2425 to 2925 fathoms.

Subgenus 2. Stylatractylis, Haeckel.

Definition.—Network of the outer shell regular, with meshes of equal size and similar form; surface thorny or papillose, covered with small spinules or tubercles.

4. Stylatractus giganteus, n. sp. (Pl. 17, fig. 1).

Amphistylus giganteus, Haeckel, 1879, Atlas (pl. xvii. fig. 1).

Cortical shell papillose, very thick walled, with regular network; pores circular, with double margin, about twice as broad as the bars; ten to twelve on the half equator. The cortical shell is connected with the outer medullary shell by numerous strong beams, and the inner prolongations of both polar spines are much stronger. The circular pores of the outer medullary shell are three times as large as those of the inner, and equal to those of the cortical shell, but the bars are much thinner. Polar spines very strong, three-sided pyramidal, with spirally contorted edges, as long as the main axis, as broad at the base as the inner medullary shell.

Dimensions.—Major axis of the cortical shell 0.3, minor axis 0.22; pores 0.02, bars 0.01; main axes of the ellipsoidal medullary shells 0.14 and 0.07; length of the polar spines 0.3, basal thickness 0.06.

Habitat.—Western Tropical Pacific, Station 225, depth 4475 fathoms.

5. Stylatractus carduus, Haeckel.

Stylosphæra carduus, Ehrenberg, 1875, Abhandl. d. k. Akad. d. Wiss. Berlin, p. 84, Taf. xxv. fig. 7.

Cortical shell thin walled, spiny, with regular, circular pores, five times as broad as the bars; ten to twelve on the half equator. Polar spines conical, half as long as the main axis, at the base broader than the pores. (The cortical shell is ellipsoidal as well as both medullary shells; the figure of Ehrenberg, as is generally the case, is more correct than his description. This interesting species occurs in the Barbados rocks, with double as well as with simple medullary shell, and may in the latter case be distinguished as Lithatractus carduelis.)

Dimensions.—Major axis of the cortical shell 0.12 to 0.16, minor 0.1 to 0.14; pores 0.01 to 0.02, bars 0.002 to 0.005; main axes of the ellipsoidal medullary shells 0.05 and 0.03; length of the polar spines 0.06, basal breadth 0.02.

Habitat.—Fossil in the Tertiary rocks of Barbados.

Subgenus 3. Stylatractona, Haeckel.

Definition.—Network of the outer shell irregular, with meshes of different size or form; surface smooth, without thorns or papillæ.

6. Stylatractus variabilis, n. sp.

Cortical shell thin walled, smooth, with irregular, roundish pores, twice to six times as broad as the bars; twelve to sixteen on the half equator. Polar spines conical, about half as long as the main axis, and as broad at the base as the inner medullary shell. (The size and form of the pores and of the polar spines in this species are very variable, so that the proportions given are to be understood as averages.)

Dimensions.—Major axis 0.13, minor axis 0.11; pores 0.004 to 0.012, bars 0.002; main axes of the ellipsoidal medullary shells 0.07 and 0.04; length of the polar spines 0.06, basal breadth 0.03.

Habitat.—Pacific, central area. Stations 272 to 274, depth 2350 to 2750 fathoms.

7. Stylatractus sethoporus, n. sp. (Pl. 17, figs. 2, 3).

Cortical shell thick walled, smooth, with large irregular, roundish pores, twice to four times as broad as the bars; seven to eight on the half equator. At the bottom of each pore a thin lamella of silex, perforated by four to six irregular, roundish, double-contoured porules. Medullary shells resemble those of Stylatractus giganteus. Polar spines three-sided pyramidal; their length and basal thickness scarcely equal the diameter of the inner medullary shell.

Dimensions.—Major axis 0.15, minor axis 0.13; pores 0.02, bars 0.005, porules 0.01; length of the polar spines 0.04.

Habitat.—Pacific, central area, Station 272, depth 2600 fathoms.

Subgenus 4. Stylatractium, Haeckel.

Definition.—Network of the outer shell irregular, with meshes of different size and form; surface thorny or papillose, covered with small spinules or tubercles.

8. Stylatractus papillosus, n. sp.

Cortical shell thin walled, with papillose surface, and irregular, simple, roundish pores, ten to sixteen on the half equator, twice to three times as broad as the bars. Conical papillæ of the surface irregularly scattered. Polar spines conical, about as long as the main axis, at the base half as broad as the inner medullary shell.

Dimensions.—Major axis 0.12, minor 0.1; pores 0.006 to 0.01, bars 0.003; main axes of the medullary shells 0.09 and 0.06; length of the polar spines 0.13, basal breadth 0.04.

Habitat.—Indian Ocean, surface (between Socotra and Ceylon), Haeckel.

9. Stylatractus disetanius, n. sp.

Cortical shell thin walled, with spiny surface, and irregular, roundish pores, eight to ten on the half equator, twice to three times as broad as the bars. Every pore is divided by thinner bars into four to six small roundish porules. Polar spines three-sided pyramidal, nearly as long as the main axis, as broad at the base as the inner medullary shell. (Resembles Xiphatractus glyptodon, Pl. 17, figs. 9, 10, but differs from it by the irregular network and the equal size of both polar spines.)

Dimensions.—Major axis 0.14, minor 0.1; pores 0.02, bars 0.008, porules 0.007; main axes of the two medullary shells 0.08 and 0.05; length of the polar spines 0.13, basal breadth 0.04.

Habitat.—South Pacific, near New Zealand, Station 169, surface.

Genus 140. Xiphatractus,^[19] n. gen.

Definition.—Druppulida with a simple ellipsoidal cortical shell and double medullary shell, in the main axis with two large opposite polar spines of different size or form.

The genus Xiphatractus differs from the nearly related Stylatractus in the differentiation of two polar spines (in the same manner as Druppatractus differs from Lithatractus). From the spherical Amphistylus it differs in the ellipsoidal form of the cortical shell.

Subgenus 1. Xiphatractara, Haeckel.

Definition.—Network of the cortical shell regular or subregular, with meshes of nearly equal size and similar form; surface smooth, without thorns or papillæ.

1. Xiphatractus armadillo, n. sp. (Pl. 17, fig. 11).

Cortical shell thick walled, smooth, with regular, circular pores, about as broad as the bars; fifteen to sixteen on the half equator. Polar spines three-sided pyramidal, with thick, prominent edges, of irregular form; the longer about as long as the main axis, the shorter scarcely one-third as long; their basal breadth equals the diameter of the inner medullary shell.

Dimensions.—Major axis of the cortical shell 0.13, minor axis 0.1, thickness of its wall 0.01; pores and bars 0.005; main axes of the two medullary shells 0.07 and 0.03; length of the major polar spine 0.12, of the minor 0.04, basal thickness 0.04.

Habitat.—Pacific, central area, Station 272, depth 2600 fathoms.

2. Xiphatractus euphractus, n. sp.

Cortical shell thick walled, smooth, with regular, circular pores, twice as broad as the bars; eight to nine on the half equator. Each pore has six to nine excisions (commonly eight), elegantly lobed, flower-like (as in Xiphostylus phasianus, Pl. 13, fig. 9). Polar spines strong, angulate; the major pyramidal, longer than the main axis, the shorter elegantly pommel-like, scarcely one-third as long.

Dimensions.—Major axis 0.15, minor 0.12; pores 0.014, bars 0.007; main axes of the two medullary shells 0.09 and 0.05; length of the larger polar spine 0.16, of the shorter 0.05, greatest thickness 0.03.

Habitat.—South Atlantic, Station 332, depth 2200 fathoms.

Subgenus 2. Xiphatractylis, Haeckel.

Definition.—Network of the cortical shell regular or subregular, with meshes of nearly equal size and similar form; surface thorny or papillose.

3. Xiphatractus spinulosus, Haeckel.

Stylosphæra spinulosa, Ehrenberg, 1875, Abhandl. d. k. Akad. d. Wiss. Berlin, p. 84, Taf. xxv. fig. 8.

Cortical shell thin walled, with spiny surface, and large, regular, circular pores, four times as broad as the bars; seven to eight on the half equator. Spines between the pores of the same size, conical. Polar spines also conical, but much larger; the major about as long as the main axis, the minor scarcely half as long; their basal thickness equals the largest pores.

Dimensions.—Major axis 0.1, minor 0.08; pores 0.012, bars 0.003; diameter of the spherical medullary shells 0.06 and 0.03; length of the major polar spine 0.09, of the minor 0.04, basal thickness 0.02.

Habitat.—Fossil in the Tertiary rocks of Barbados.

4. Xiphatractus sulcatus, Haeckel.

Stylosphæra sulcata, Ehrenberg, 1875, Abhandl. d. k. Akad. d. Wiss. Berlin, p. 84, Taf. xxiv, fig. 6.

Cortical shell thick walled, with thorny surface, and regular, circular pores, quite as broad as the bars; nine to ten on the half equator. Polar spines cylindrical, with longitudinal basal furrows and conical apex, three times as broad as the pores; the larger about as long as the main axis, the shorter only one-half or two-thirds as long.

Dimensions.—Major axis 0.01, minor 0.08; pores and bars 0.007; main axes of the two medullary shells 0.08 and 0.04; length of the major polar spine 0.1, of the minor 0.06, breadth of them 0.02.

Habitat.—Fossil in the Barbados deposits.

5. Xiphatractus dasypus, n. sp.

Cortical shell thick walled, with spiny surface, and regular, elegant network; pores circular, hexagonally framed, about as broad as the bars; from every corner of the network (between three pores) arises a short bristle-like spine. Polar spines three-sided prismatic, as broad as one hexagon; the major once to twice as long as the main axis, the minor only one-half to one-fourth as long. (The cortical shell much resembles Ellipsoxiphus elegans, Pl. 14, fig. 7.)

Dimensions.—Major axis 0.15, minor 0.13; pores and bars 0.01; main axes of the two medullary shells 0.1 and 0.06; length of the major polar spine 0.1 to 0.3, of the minor 0.05 to 0.1, thickness 0.01.

Habitat.—Tropical Western Pacific, Station 222, surface.

Subgenus 3. Xiphatractona, Haeckel.

Definition.—Network of the cortical shell irregular, with meshes of different size or form; surface smooth, without thorns or papillæ.

6. Xiphatractus chlamydophorus, n. sp.

Cortical shell thin walled, smooth, with irregular, roundish pores, twice to four times as broad as the bars; eight to twelve on the half equator. Polar spines angular, irregularly curved or contorted; the larger once to twice as long as the main axis, the shorter and thicker pommel-shaped, only one-third to one-half as long; their basal breadth equals two pores.

Dimensions.—Major axis 0.14, minor 0.1; pores 0.006 to 0.012, bars 0.003; main axis of the two ellipsoidal medullary shells 0.09 and 0.04; length of the major polar spine 0.1 to 0.2, of the minor 0.05 to 0.08, breadth 0.02.

Habitat.—Cosmopolitan; Atlantic, Pacific, many Stations, surface.

Subgenus 4. Xiphatractium, Haeckel.

Definition.—Network of the cortical shell irregular, with meshes of unequal size or dissimilar form; surface thorny or papillose.

7. Xiphatractus radiosus, Haeckel.

Stylosphæra radiosa, Ehrenberg, 1875, Abhandl. d. k. Akad. d. Wiss. Berlin, p. 84, Taf. xxiv. fig. 5.

Cortical shell very thick walled, with thorny surface, and irregular, roundish pores, once to three times as broad as the bars; nine and ten on the half equator. Polar spines conical, on the base about as broad as the largest pores; the larger as long as the main axis, the smaller scarcely one-fourth as long. (The radial striation, figured by Ehrenberg and applied to the name of this species, is produced by the contours of the funnel-shaped pores in the thick walls seen in optical section; the ellipsoidal cortical shell is double.)

Dimensions.—Major axis 0.13, minor 0.09; pores 0.003 to 0.01, bars 0.003; main axes of the two medullary shells 0.05 and 0.03; length of the major polar spine 0.12, of the minor 0.03, basal breadth 0.01.

Habitat.—Fossil in the Tertiary rocks of Barbados.

8. Xiphatractus glyptodon, n. sp. (Pl. 17, figs. 9, 10).

Cortical shell thick walled, covered with radial spines of the size of the pores; on the half equator eight to ten irregular or subregular roundish pores, twice to four times as broad as the bars. In the bottom of each pore a thin lamella of silex, perforated by four to six smaller roundish pores. Both medullary shells (fig. 10) spherical, with smaller, regular, circular pores. Larger polar spine three-sided pyramidal, in length equals the main axis; shorter spine only half as long, but twice as thick, of elegant pommel-form (fig. 9), with nine prominent edges.

Dimensions.—Major axis 0.12, minor, 0.1; pores and spines 0.01 to 0.02, bars and porules 0.005; diameter of the two medullary shells 0.05 and 0.02; length of the major polar spine 0.1, of the minor 0.06, greatest thickness 0.04.

Habitat.—Pacific, central area, Station 263, surface.

Genus 141. Cromyatractus,^[20] n. gen.

Definition.—Druppulida with four or more concentric shells (two medullary shells and two or more cortical shells), in the main axis with two large opposite polar spines of equal size and similar form.

The genus Cromyatractus is very nearly allied to all the foregoing genera, which bear two equal spines opposite to one another on the poles of the main axis; it differs from them in the multiplication of the cortical shell, and may be considered as the most highly developed form of this amphistylous series, which proceeds from Ellipsoxiphus to Lithatractus and Stylatractus.

Subgenus 1. Cromyatractium, Haeckel.

Definition.—Shell composed of two medullary shells and two cortical shells.

1. Cromyatractus tetraphractus, n. sp. (Pl. 15, fig. 2).

Stylocromium tetraphractum, Haeckel, 1879, Atlas (pl. xv. fig. 2).

Proportion of the main axes of the four concentric shells about = 1 : 3 : 5 : 7. Network of all four shells nearly of the same structure, subregular, with circular pores of equal size (in one and the same shell). The absolute size of the pores increases gradually from the innermost to the outermost shell. The bars between the pores are smaller and quite smooth. Surface of the outermost shell smooth. Polar spines cylindrical, with conical apex, of variable length, nearly as broad as the innermost shell.

Dimensions.—Main axes of the four shells—(A) inner medullary shell 0.03, (B) outer medullary shell 0.08, (C) inner cortical shell 0.15, (D) outer cortical shell 0.2; equatorial axes of them—(A) 0.025, (B) 0.06, (C) 0.12, (D) 0.15; pores of (A) 0.004, (B) 0.007, (C) 0.01, (D) 0.013, bars 0.002 to 0.004; length of the polar spines 0.1 to 0.3 (and more), breadth 0.015.

Habitat.—Antarctic (Indian) Ocean, Station 157, depth 1950 fathoms.

2. Cromyatractus tetralepas, n. sp.

Proportion of the main axes of the four concentric shells about = 1 : 2 : 4 : 6. Network of the two medullary shells regular, with small circular pores, little larger than the bars. Network of the two cortical shells irregular, with much larger polygonal pores, three to nine times as broad as the thin bars. (Somewhat similar to Cromyatractus ceparius, Pl. 15, fig. 4.) Surface of the outermost shell smooth or a little thorny. Polar spines cylindrical, very large, twice to three times as long as the main axis of the outermost shell, about as broad as the innermost shell, with conical apex; smooth or a little thorny.

Dimensions.—Main axes of the four shells—(A) 0.03, (B) 0.05, (C) 0.13, (D) 0.18; equatorial axes of them—(A) 0.2, (B) 0.45, (C) 0.11, (D) 0.14; pores of the two medullary shells 0.004 and 0.006, of both cortical shells 0.01 to 0.03, bars 0.003.

Habitat.—Indian Ocean, Zanzibar, Pullen, 2200 fathoms.

3. Cromyatractus tetracelyphus, n. sp. (Pl. 15, figs. 1, 1a).

Proportion of the main axes of the four concentric shells about = 1 : 3 : 10 : 11. Network of the two spherical medullary shells (fig. 1a) regular, with small circular pores, twice as broad as the bars. Network of the inner cortical shell regular with circular, hexagonally-framed pores, twice as broad as the bars. From every corner of the hexagons (between three pores) arises a very thin, hair-like, short radial spinule. These spinules communicate with one another by tangential branches (at equal distances from the inner cortical shell), and form thereby an outer, delicate cortical network, with large polygonal meshes and very thin bars. Polar spines very strong, pyramidal, with prominent edges, as long as the main radius of the cortical shell, and half as broad at the base.

Dimensions.—Main axes of the four shells—(A) 0.02, (B) 0.06, (C) 0.2, (D) 0.22; equatorial axes of them—(A) 0.02, (B) 0.06, (C) 0.13, (D) 0.15; pores of the four shells—(A) 0.002, (B) 0.004, (C) 0.008, (D) 0.02; bars 0.001 to 0.003; length of the polar spines 0.1, basal breadth 0.05.

Habitat.—South Atlantic, Station 335, depth 1425 fathoms.

Subgenus 2. Caryatractus, Haeckel.

Definition.—Shell composed of two medullary shells and three or more cortical shells.

4. Cromyatractus cepicius, n. sp. (Pl. 15, fig. 3).

Caryostylus cepicius, Haeckel, 1879, Atlas (pl. xv. fig. 3). Caryodoras cepicius, Haeckel, 1881, Prodromus, p. 454.

Proportion of the main axes of the five concentric shells about = 1 : 2 : 5 : 7 : 8. Network of both spherical medullary shells regular, with small circular pores, about as broad as the bars. Network of the three ellipsoidal cortical shells irregular, with large polygonal meshes, five to ten times as broad as the thin bars. Surface of the outermost shell smooth. Polar spines cylindrical, thorny, about as thick as the innermost shell and as long as the outermost shell, against the apex with a spindle-like intumescence, formed by delicate spongy framework (fig. 3).

Dimensions.—Main axes of the five concentric shells—(A) 0.03, (B) 0.05, (C) 0.16, (D) 0.2, (E) 0.25; equatorial axes of them—(A) 0.03, (B) 0.05, (C) 0.12, (D) 0.16, (E) 0.2; pores of the two medullary shells 0.002 to 0.004, of the three cortical shells 0.02 to 0.04, bars 0.002; length of the polar spines 0.3, breadth 0.03.

Habitat.—Pacific, central area, Station 268, depth 2900 fathoms.

5. Cromyatractus ceparius, n. sp. (Pl. 15, fig. 4).

Caryostylus ceparius, Haeckel, 1881, Prodromus et Atlas (pl. xv. fig. 4).

Proportion of the main axes of the six concentric shells about = 1 : 2 : 7 : 10 : 13 : 18. Network of the three inner shells regular, with small, circular pores, which are about as broad as the bars and in the third shell hexagonally framed. Network of the three outer shells irregular, with large polygonal meshes, six to twelve times as broad as the bars. Surface smooth. Polar spines strong, spindle-shaped, thorny, outside of the sixth shell about as long as inside of it; broader than the innermost shell; the thorns of their outer free part (arising at equal distances) represent perhaps the beginnings of three to four further shells.

Dimensions.—Main axes of the six concentric shells—(A) 0.02, (B) 0.05, (C) 0.14, (D) 0.2, (E) 0.26, (F) 0.37; equatorial axes—(A) 0.02, (B) 0.05, (C) 0.09, (D) 0.15, (E) 0.21, (F) 0.3; pores of the three inner shells 0.003 to 0.006, of the three outer shells 0.02 to 0.04, bars 0.003 to 0.005; length of the polar spines, from the base of the innermost shell to the apex, 0.35, greatest breadth 0.03.

Habitat.—South Pacific, Station 285, depth 2375 fathoms.

Genus 142. Pipetta,^[21] n. gen.

Definition.—Druppulida with simple ellipsoidal cortical shell and simple medullary shell, with two hollow fenestrated tubes opposite on both poles of the main axis.

The genus Pipetta differs from Pipettella (p. 304) in the possession of an inner (medullary) shell; it exhibits the same tubular prolongations of the cortical shell at both poles of the main axis.

1. Pipetta fusus, n. sp. (Pl. 39, figs. 8, 8a).

Cortical shell spindle-shaped, the middle ellipsoidal part gently passing over on both poles into the conical tubes, which attain about the same length. Network regular, with circular, hexagonally-framed pores, twice as broad as the bars, sixteen to eighteen on the half equator. In the middle part of the shell the pores arise from their hexagonal bases in the form of short conical funnels; on both tubes they are much smaller and simple, without frame. Medullary shell (fig. 8a) spherical, scarcely one-third as broad as the cortical, with regular, circular pores, twice as broad as the bars, eight to nine on the half equator. The two shells are connected only by two opposite beams, lying in the equatorial axis and ramified at the distal insertion (fig. 8a).

Dimensions.—Middle ellipsoidal part of the cortical shell 0.13 to 0.15; polar tubes 0.15 long, 0.06 broad at the base; pores of the former 0.01, bars 0.005; pores of the tubes 0.06, bars 0.003. Medullary shell 0.04, pores 0.004, bars 0.002.

Habitat.—Pacific, central area, Station 268, depth 2900 fathoms.

2. Pipetta tuba, n. sp. (Pl. 39, fig. 7).

Cortical shell nearly spherical in the middle part, which is sharply separated at both poles from the long, nearly cylindrical tubes; these are longer than the main axis, at the distal end open (always broken off). Network regular, with circular, hexagonally-framed pores, of the same breadth as the bars, eighteen to twenty on the half equator. The pores of the polar tubes are of the same shape, only much smaller, and arranged in sixteen to eighteen longitudinal rows. Medullary shell spherical, about one-third as broad as the cortical, with simple circular pores. The connection between the two shells is only made by two simple opposite beams, lying in the equatorial axis.

Dimensions.—Middle spheroidal part of the cortical shell 0.14 to 0.16; polar tubes 0.15 to 0.2 or longer, 0.03 broad; pores and bars of the former 0.007, of the latter 0.003. Medullary shell 0.04, pores 0.006, bars 0.003.

Habitat.—Western Tropical Pacific, Station 225, depth 4475 fathoms.

3. Pipetta salpinx, n. sp.

Cortical shell ellipsoidal, sharply separated from the cylindrical polar tubes, which reach about the same length (or more). Network regular, with circular pores, three times as broad as the bars, without hexagonal frames, fourteen to fifteen on the half equator. Pores of the polar tubes smaller, arranged in eight to ten longitudinal rows. Medullary shell spherical, one-fourth as broad as the cortical, connected with it by a circle of four to six radial beams, lying in the equatorial plane. Differs from Pipettella prismatica (Pl. 39, fig. 6) in the possession of a medullary shell and the absence of the tube edges.

Dimensions.—Main axis of the ellipsoid 0.14, equatorial axis 0.12, pores 0.01, bars 0.003; length of the tubes 0.15 or more, breadth 0.03. Medullary shell 0.03, pores 0.002, bars 0.001.

Habitat.—Pacific, central area, Stations 265 to 268, depth 2700 to 2900 fathoms.

4. Pipetta conus, n. sp.

Cortical shell spindle-shaped, the middle ellipsoidal part gently passing over at both poles into the conical tubes, which attain only half its length. Network irregular, with roundish or subcircular pores, twice to three times as broad as the bars, twelve to sixteen on the half equator. Medullary shell spherical, one-fourth as broad as the cortical. (Differs from the foregoing species in the short conical tubes and the irregular reticulation.)

Dimensions.—Middle part of the cortical shell 0.16 long, 0.13 broad; tubes 0.09 long, 0.05 on the base broad; pores 0.005 to 0.01, bars 0.003. Medullary shell 0.04.

Habitat.—North Pacific, Station 241, depth 2300 fathoms.

Genus 143. Pipettaria,^[22] n. gen.

Definition.—Druppulida with simple ellipsoidal cortical shell and double medullary shell, with two hollow fenestrated tubes opposite on both poles of the main axis.

The genus Pipettaria differs from the foregoing Pipetta only in the duplication of the medullary shell; as in this, the tubular prolongations of the main axis of the cortical shell may be either conical (with closed apex) or cylindrical (with apical opening?).

1. Pipettaria fusaria, n. sp.

Cortical shell spindle-shaped, the middle ellipsoidal part gently passing over on both poles into the conical tubes, which attain about half its length. Pores regular, circular, twice as broad as the bars, sixteen to eighteen on the half equator; pores of the tubes smaller. Both medullary shells spheroidal, compressed. (The appearance of the cortical shell resembles that of Cannartiscus amphiconus, Pl. 39, fig. 19, but without the equatorial constriction.)

Dimensions.—Main axis of the ellipsoid 0.15, equatorial axis 0.13; length of the polar tubes 0.08, basal breadth 0.05; pores of the former 0.008, bars 0.004; diameter of the medullary shells 0.04 and 0.02.

Habitat.—South Pacific, Station 300, depth 1375 fathoms.

2. Pipettaria tubaria, n. sp. (Pl. 39, fig. 15).

Cannartidium tubarium, Haeckel, 1882, Atlas (pl. xxxix. fig. 15).

Cortical shell ellipsoidal, on both poles distinctly separated from the short conical tubes, the length and breadth of which equal the outer medullary shell. In the equatorial plane arises a circle of four to six short conical protuberances, similar to the polar tubes. Pores subregular, circular, or roundish, scarcely broader than the bars, sixteen to twenty on the half equator. Both medullary shells spheroidal, somewhat compressed in the direction of the two poles (as in fig. 18a).

Dimensions.—Main axis of the ellipsoid 0.12, equatorial axis 0.09; pores 0.005, bars 0.004; size of the equatorial protuberances and of the polar tubes 0.02.

Habitat.—Pacific, central area, Station 265, depth 2900 fathoms.

Family XIII. Spongurida, Haeckel (Pl. 48, figs. 6, 7).

Spongurida, Haeckel, 1862, Monogr. d. Radiol., p. 447 (sensu emendato).

Definition.—Prunoidea with spongy ellipsoidal or cylindrical shell, composed wholly or partially of a spongy framework, without equatorial stricture, with or without an enclosed medullary shell.

The family Spongurida comprises, in the sense here restricted, all those Prunoidea in which the ellipsoidal or cylindrical shell is composed wholly or partially of an irregular siliceous framework, not of simple lattice-work. It contains two subfamilies, differing in the absence or presence of a latticed medullary shell in the middle of the central capsule; in the Spongellipsida it is absent, in the Spongodruppida present; the former are most nearly related to the Ellipsida, the latter to the Druppulida, the difference consisting only in the spongy structure of the cortical shell.

In my Monograph (1862, p. 447) the family Spongurida had a much wider extent, comprising also a number of Sphæroidea and Discoidea, agreeing in the spongy structure of the shell. Here we restrict the definition to those spongy Sphærellaria in which the central capsule and the enclosing spongy cortical shell are ellipsoidal or cylindrical, therefore each transverse section is a circle, and each meridional section an ellipse, as in all Prunoidea.

The Cortical Shell in all Spongurida is composed of a delicate framework of irregularly branched and interwoven siliceous threads; commonly this spongy structure is rather dense or compact, but sometimes also very loose. In the simplest form, Spongellipsis, the spongy cortical shell contains a large cavity, in which lies freely the central capsule. In Spongurus this cavity is completely distended by a spongy framework. In this case the solid spongy shell becomes often prolonged, and its original ellipsoidal form passes over into a cylindrical one (as in many Zygartida). Sometimes (particularly in Spongocore, Pl. 48, fig. 6) the cylinder becomes three-jointed by two more or less distinct annular constrictions. Spongocore is distinguished by an outer veil, a thin lattice-lamella, which envelops the spongy shell and is connected with it by radial beams.

The Medullary Shell, absent in the Spongellipsida, is constant in the second subfamily Spongodruppida. It is either a simple latticed shell (Spongodruppa) or double, composed of two concentric latticed shells (Spongoliva); its form is either spherical or ellipsoidal. It lies in the middle of the central capsule, and is connected by radial beams (perforating the membrane of the latter) with the enveloping spongy cortical shell.

In many Spongurida the surface of the shell is armed with radial spines, and in some genera (Spongoprunum, Spongatractus, &c., Pl. 17, fig. 12), on both poles of the main axis, are developed two strong opposite polar spines, as in many other Prunoidea.

The Central Capsule of the Spongurida is either ellipsoidal or cylindrical. Only in Spongellipsis it lies freely in the internal cavity of the spongy shell. In all other genera it is perforated by a part of the skeleton; in the Spongodruppida it contains the simple or double medullary shell, and the radial beams which perforate its membrane and connect the latter with the external spongy cortical shell. In Spongurus and the allied genera (Spongocore, Spongoprunum) the whole central capsule is filled with a spongy framework which also envelops its surface.

Synopsis of the Genera of Spongurida.

I. Subfamily Spongellipsida. (Ellipsoidal shell composed only of a spongy framework without a latticed medullary shell in the centre.	$\scriptstyle {\left\{{\begin{matrix}\ \\\\\ \\\ \\\ \\\ \\\ \\\ \\\ \\\ \ \end{matrix}}\right.}$	Spongy shell with internal cavity.	$\scriptstyle {\left.{\begin{matrix}\ \\\ \end{matrix}}\right\}\,}$	No polar spines,	144. Spongellipsis.
		Spongy shell solid, without internal cavity.	$\scriptstyle {\left\{{\begin{matrix}\ \\\\\ \\\ \\\ \\\ \\\ \\\ \ \end{matrix}}\right.}$	Without lattice mantle. No polar spines,	145. Spongurus.
				With lattice mantle. No polar spines,	146. Spongocore.
				Without lattice mantle. Two opposite spines on the poles of the axis,	147. Spongoprunum
II. Subfamily Spongodruppida. (Ellipsoidal shell composed of an outer spongy cortical shell and an inner latticed medullary shell.)	$\scriptstyle {\left\{{\begin{matrix}\ \\\\\ \\\ \\\ \\\ \\\ \ \end{matrix}}\right.}$	Medullary shell simple.	$\scriptstyle {\left\{{\begin{matrix}\ \\\\\ \ \end{matrix}}\right.}$	No polar spines,	148. Spongodruppa.
				Two opposite spines on the poles of the axis,	149. Spongatractus.
		Medullary shell double.	$\scriptstyle {\left\{{\begin{matrix}\ \\\\\ \ \end{matrix}}\right.}$	No polar spines,	150. Spongoliva.
				Two opposite spines on the poles of the axis,	151. Spongoxiphus.

Subfamily 1. Spongellipsida, Haeckel.

Definition.—Spongurida with a spongy ellipsoidal or cylindrical shell, without an internal latticed medullary shell.

Genus 144. Spongellipsis,^[23] n. gen.

Definition.—Spongurida with an ellipsoidal or cylindrical spongy shell, containing an internal cavity, without a latticed medullary shell. Polar spines absent.

The genus Spongellipsis embraces those very simple Spongurida in which the ellipsoidal central capsule is enclosed in a spongy cortical shell of the same form. It corresponds, therefore, to Plegmosphæra among the Sphæroidea, to Plegmodiscus among the Discoidea, and to Spongolarcus among the Larcoidea. In some species the ellipsoidal form is prolonged and passes into a cylindrical one.

Subgenus 1. Spongellipsarium, Haeckel.

Definition.—Surface of the shell smooth or rough, without radial spines.

1. Spongellipsis lævis, n. sp.

Shell ellipsoidal, with smooth surface, its spongy wall scarcely one-tenth as thick as the minor axis of the inner cavity. Spongy framework very compact, with small meshes, three to six times as broad as the bars. Proportion of the major axis to the minor = 3 : 2.

Dimensions.—Major axis (or length) of the shell 0.36, minor axis (or breadth) 0.24.

Habitat.—Pacific, central area, Station 265, surface.

2. Spongellipsis aspera, n. sp.

Shell ellipsoidal, with rough surface, its spongy wall nearly half as thick as the minor axis of the inner cavity. Spongy framework very loose, with large meshes, ten to twenty times as broad as the bars. Proportion of the major axis to the minor = 4 : 3.

Dimensions.—Length of the shell 0.24, breadth 0.18.

Habitat.—North Pacific, Station 253, surface.

3. Spongellipsis aplysina, n. sp.

Shell nearly cylindrical, with rough surface, its spongy wall about one-fourth as thick as the minor axis of the internal cavity. Spongy framework loose, with large meshes, four to eight times as broad as the bars. Proportion of both axes = 6 : 1. (Similar to a spongy cylinder of Aplysina.)

Dimensions.—Length of the shell 0.3, breadth 0.05.

Habitat.—North Atlantic, Station 64, surface.

Subgenus 2. Spongellipsidium, Haeckel.

Definition.—Surface of the shell covered with radial spines.

4. Spongellipsis setosa, n. sp.

Shell ellipsoidal, covered with numerous (sixty to eighty) thin, bristle-shaped, radial spines, about half as long as the major axis. Spongy framework loose, with large meshes, ten to twenty times as broad as the bars. Minor axis of the inner cavity twice as long as the thickness of the spongy wall. Proportion of both axes = 5 : 3.

Dimensions.—Length of the shell 0.2, breadth 0.12.

Habitat.—South Atlantic, Station 325, surface.

5. Spongellipsis spinosa, n. sp.

Shell nearly cylindrical, covered with numerous thorns and thirty to forty larger conical radial spines, somewhat longer than the major axis. Spongy framework compact, with small meshes, four to eight times as broad as the bars. Minor axis of the inner cavity about six times as large as the thickness of the spongy wall. Proportion of both axes = 4 : 1.

Dimensions.—Length of the shell 0.24, breadth 0.06.

Habitat.—South Pacific, Station 300, surface.

Genus 145. Spongurus,^[24] Haeckel, 1862, Monogr. d. Radiol., p. 465.

Definition.—Spongurida with ellipsoidal or cylindrical (sometimes three-jointed) shell, of solid spongy framework, without internal cavity and without latticed medullary shell. Polar spines and outer lattice-mantle absent.

The genus Spongurus was founded by me in 1862 for the common cosmopolitan Spongurus cylindricus, a massive spongy cylinder with radial spines. I enlarge here the conception of the genus, in receiving also ellipsoidal, massive spongy Prunoidea, with or without radial spines. Sometimes the cylindrical shell is more or less distinctly three-jointed, with two annular strictures, as also in the following and nearly allied genus.

Subgenus 1. Spongurantha, Haeckel.

Definition.—Spongy framework everywhere of the same structure; surface smooth or rough, but without radial spines.

1. Spongurus stuparius, n. sp.

Shell ellipsoidal, one and a half times as long as broad, with nearly smooth surface. Spongy framework everywhere of equal structure, with small meshes, four to six times as broad as the bars.

Dimensions.—Length of the shell (or major axis) 0.2, breadth of it (or minor axis) 0.14.

Habitat.—South Pacific, Station 295, depth 1500 fathoms.

2. Spongurus stypticus, n. sp.

Shell ellipsoidal, twice as long as broad, with thorny surface. Spongy framework everywhere of equal structure, with large meshes, ten to twenty times as broad as the bars.

Dimensions.—Length of the shell 0.3, breadth 0.15.

Habitat.—Pacific, central area, Station 274, depth 2750 fathoms.

3. Spongurus phalanga, Haeckel.

Spongurus cylindricus, Stöhr, 1880, Palæontogr., vol. xxvi. p. 119, Taf. vii. fig. 3.

Shell nearly cylindrical, five times as long as broad, with thorny surface. Spongy framework compact, everywhere of equal structure, with small meshes, scarcely broader than the bars.

Dimensions.—Length of the shell 0.24, breadth 0.05.

Habitat.—Pacific, central area, Station 268, depth 2600 fathoms; fossil in the Tertiary rocks of Sicily, Stöhr.

Subgenus 2. Spongurella, Haeckel.

Definition.—Spongy framework everywhere of the same structure; surface armed with radial spines.

4. Spongurus asper, Haeckel.

Haliomma asperum, Joh. Müller, 1858, Abhandl. d. k. Akad. d. Wiss. Berlin, p. 40, Taf. ii. fig. 2. Haliomma asperum, Haeckel, 1862, Monogr. d. Radiol., p. 431.

Shell ellipsoidal, one and a third times as long as broad, with thorny surface and twenty symmetrically disposed, thin, bristle-shaped, radial spines, about as long as the shell. Spongy framework everywhere of the same structure, very compact, with small meshes, three to four times as broad as the bars.

Dimensions.—Length of the shell 0.11, breadth 0.08.

Habitat.—Mediterranean, Ligurian coast (J. Müller), Portofino (Haeckel).

5. Spongurus cylindricus, Haeckel.

Spongurus cylindricus, Haeckel, 1862, Monogr. d. Radiol., p. 465, Taf. xxvii. fig. 1.

Shell cylindrical, four to five times as long as broad, with nearly smooth surface, and twenty to thirty thin, bristle-shaped, radial spines, about half as long as the shell. Spongy framework everywhere of the same structure, very compact, with small meshes, scarcely broader than the bars.

Dimensions.—Length of the shell 0.2, breadth 0.04 to 0.05.

Habitat.—Cosmopolitan; Mediterranean, Atlantic, and Pacific, surface.

6. Spongurus tricolus, n. sp.

Shell nearly cylindrical, with two slight annular transverse strictures; its middle part is somewhat broader. Surface thorny, with numerous (forty to sixty or more) short, thin, radial spines, not longer than the breadth of the shell. Spongy framework everywhere of the same structure, compact, with small meshes, twice to three times as broad as the bars.

Dimensions.—Length of the shell 0.24, breadth 0.04 to 0.06.

Habitat.—Pacific, central area, Station 272, 2600 fathoms.

Subgenus 3. Sponguroma, Haeckel.

Definition.—Spongy framework in the inner part of the shell very compact, in the outer part very loose; surface armed with radial spines.

7. Spongurus radians, n. sp.

Shell ellipsoidal, one and a half times as long as broad, with thorny surface, and eighty to one hundred and twenty (or more) thin, bristle-shaped, radial spines, somewhat longer than the shell. Spongy framework in the inner part very compact, in the outer part very loose, with a gradual transition between the two parts. Meshes in the central part not broader than the bars, in the superficial part ten to twenty times as broad.

Dimensions.—Length of the shell 0.24, breadth 0.16.

Habitat.—Mediterranean, Portofino, near Genoa, Haeckel, surface.

8. Spongurus spongechinus, n. sp.

Shell ellipsoidal, one and a third times as long as broad, with thorny surface, and thirty to forty thick, conical radial spines, about half as long as the shell. Spongy framework in the inner part of the shell compact, in the outer loose, with a gradual transition between the two parts. Meshes in the central part smaller than the bars, in the superficial part four to eight times as broad.

Dimensions.—Length of the shell 0.18, breadth 0.14.

Habitat.—North Atlantic, Station 353, surface.

Genus 146. Spongocore,^[25] n. gen.

Definition.—Spongurida with ellipsoidal or cylindrical (sometimes three-jointed) shell of solid spongy framework, without internal cavity and without latticed medullary shell. Polar spines absent. An outer lattice-mantle is connected with the spongy shell by radial beams.

The genus Spongocore contains some widely distributed Spongurida, which are distinguished from the nearly related Spongurus by the development of a peculiar veil or mantle of delicate lattice-work, which envelops either the whole shell or only the middle part of it, and is connected with it by numerous radial beams. The distance of the simple fine lattice-lamella from the spongy shell is everywhere the same. Often the cylindrical shell is three-jointed, with two annular strictures, as also in the foregoing Spongurus. It is derived from the latter by development of the veil connecting the points of the radial spines.

Subgenus 1. Spongocorina, Haeckel.

Definition.—Shell without distinct annular strictures, not evidently three-jointed.

1. Spongocore velata, n. sp.

Shell ellipsoidal, one and a half times as long as broad, without annular strictures. Spongy framework loose, with rather large meshes, four to six times as broad as the bars. The whole spongy shell enveloped by a delicate veil with smooth surface, connected with it by numerous thin radial beams. Breadth of the spongy ellipsoid (or minor axis) six times as large as its distance from the veil.

Dimensions.—Length of the whole shell (with veil) 0.3, breadth 0.2; distance of the veil from the spongy ellipsoid 0.035.

Habitat.—South Atlantic, Station 325, surface.

2. Spongocore diplocylindrica, n. sp.

Shell cylindrical, three times as long as broad, without annular strictures. Spongy framework compact, with small meshes, twice to three times as broad as the bars. The whole surface of the spongy cylinder, with exception of both rounded polar faces, enveloped by a delicate cylindrical veil with smooth surface, connected with it by numerous radial beams. Diameter of the spongy cylinder twice as large as its distance from the veil.

Dimensions.—Length of the shell 0.3, breadth (with veil) 0.1; distance of the veil 0.025.

Habitat.—South Pacific, Station 302, surface.

Subgenus 2. Spongocorisca, Haeckel.

Definition.—Shell distinctly three-jointed, with two transverse annular strictures.

3. Spongocore chrysalis, n. sp.

Spongy shell cylindrical, without the veil six times as long as broad, three-jointed, with two annular strictures; all three joints of the same length. The whole spongy shell enveloped by a thin veil with thorny surface, connected with it by numerous radial beams. Breadth of the spongy cylinder three times as large as its distance from the veil.

Dimensions.—Length of the shell (with veil) 0.4, breadth 0.1; distance of the veil from the spongy shell 0.02.

Habitat.—South Atlantic (off Patagonia), Station 318, surface.

4. Spongocore cincta, n. sp.

Spongy shell cylindrical, without the veil four times as long as broad, three-jointed, with two annular strictures; all three joints of the same length. Only the middle joint enveloped by a thin veil with smooth surface, connected with it by radial beams. Both terminal joints with long, bristle-shaped, radial spines. Breadth of the spongy cylinder twice as large as its distance from the veil.

Dimensions.—Length of the shell 0.24, breadth (with veil) 0.12; distance of the veil 0.03.

Habitat.—Indian Ocean, Madagascar, Rabbe, surface.

5. Spongocore pupula, n. sp.

Spongy shell cylindrical, without the veil six times as long as broad, three-jointed, with two annular strictures; the middle joint half as long as either terminal joint. Only the middle joint enveloped by a thin veil with spiny surface, connected with it by twenty to thirty radial beams, which are prolonged on the outside into short radial spines. Breadth of the spongy cylinder about equal to its distance from the veil.

Dimensions.—Length of the shell 0.2, breadth (with veil) 0.1; distance of the veil 0.033.

Habitat.—North Pacific, Station 244, surface.

6. Spongocore puella, n. sp. (Pl. 48, fig. 6).

Spongy shell cylindrical, without the veil five times as long as broad, three-jointed, with two annular strictures; the middle joint twice as long as either terminal joint. Only the middle joint enveloped by a thin veil with delicate lattice-work and smooth surface; both terminal joints armed with numerous thin, bristle-shaped, radial spines. Breadth of the spongy cylinder twice as large as the distance from the veil.

Dimensions.—Length of the shell 0.25 to 0.3, breadth (with veil) 0.1 to 0.12; distance of the veil 0.028 to 0.032.

Habitat.—South Pacific, Stations 295 to 304, surface.

Genus 147. Spongoprunum,^[26] n. gen.

Definition.—Spongurida with ellipsoidal or cylindrical shell of solid spongy framework, without internal cavity and without latticed medullary shell. On the poles of the axis occur two opposite strong spines.

The genus Spongoprunum differs from the most nearly allied Spongurus by the possession of two strong solid spines, lying in the axis of the ellipsoidal or cylindrical massive spongy shell, on its two opposite poles. Spongoprunum bears therefore the same relation to Spongurus that Ellipsoxiphus does to Cenellipsis.

1. Spongoprunum amphilonche, n. sp. (Pl. 48, fig. 7).

Shell ellipsoidal, two and a third times as long as broad, with nearly smooth surface. Spongy framework very compact, in the whole solid shell of the same structure, with very small meshes, scarcely broader than the bars. Two polar spines conical, very strong, about half as long as the main axis of the shell and three times as long as broad.

Dimensions.—Length of the shell (without spines) 0.2, breadth 0.08.

Habitat.—Central Pacific, Station 265, depth 2900 fathoms; fossil in the rocks of Barbados.

2. Spongoprunum atractus, n. sp.

Shell spindle-shaped, twice as long as broad, with thorny surface. Spongy framework loose, in the whole shell of the same structure, with large meshes, eight to twelve times as broad as the bars. Two polar spines angular, pyramidal, very strong, about one-third as long as the shell, and twice as long as broad.

Dimensions.—Length of the shell 0.2, breadth 0.11.

Habitat.—Western Tropical Pacific, Station 225, depth 4475 fathoms.

3. Spongoprunum amphicylindrus, n. sp.

Shell nearly cylindrical, four times as long as broad, with rough surface. Spongy framework compact, in the whole shell of equal structure, with small meshes, twice to three times as broad as the bars. Two polar spines cylindrical, very large, longer than the shell, and about one-fourth as thick as its diameter.

Dimensions.—Length of the shell 0.2, breadth 0.05.

Habitat.—South Atlantic, Station 333, surface.

Subfamily Spongodruppida, Haeckel.

Definition.—Spongurida with latticed medullary shell, enclosed by a spongy cortical shell.

Genus 148. Spongodruppa,^[27] n. gen.

Definition.—Spongurida with spongy ellipsoidal cortical shell, enclosing a simple, spherical or ellipsoidal, latticed medullary shell. Polar spines absent.

The genus Spongodruppa opens the series of Spongodruppida, or of those Spongurida in which the ellipsoidal spongy cortical shell encloses a simple or double, latticed, medullary shell. In Spongodruppa, the simplest and probably the ancestral form of this subfamily, the medullary shell is simple and the polar spines absent. It may be derived from Druppula by a spongy thickening of the simple latticed cortical shell.

Subgenus 1. Spongodruppula, Haeckel.

Definition.—Surface of the shell smooth or rough, without radial spines.

1. Spongodruppa terebintha, n. sp.

Cortical shell one and a third times as long as broad, with smooth surface, three times as broad as the spherical medullary shell. Spongy framework very compact, with small meshes of the same breadth as the bars. Thickness of the spongy wall equal to the radius of the medullary shell.

Dimensions.—Length of the cortical shell (or major axis of the ellipsoid) 0.16, breadth (or minor axis) 0.12; thickness of its wall 0.02; medullary shell 0.04.

Habitat.—Western Tropical Pacific, Station 225, depth 4475 fathoms.

2. Spongodruppa pistacia, n. sp.

Cortical shell one and a half times as long as broad, with thorny surface, nearly five times as broad as the spherical medullary shell. Spongy framework compact, its thickness equal to the diameter of the medullary shell.

Dimensions.—Length of the cortical shell 0.2, breadth 0.14; thickness of its wall 0.03; medullary shell 0.03.

Habitat.—Fossil in the rocks of Barbados.

3. Spongodruppa lentisca, n. sp.

Cortical shell twice as long as broad, with rough surface, four times as large as the ellipsoidal medullary shell. Spongy framework loose, with large meshes, its thickness equal to the length of the medullary shell.

Dimensions.—Length of the cortical shell 0.25, breadth 0.13; thickness of its wall 0.06; length of the medullary shell 0.06, breadth 0.04.

Habitat.—Pacific, central area, Station 266, surface.

Subgenus 2. Spongodruppium, Haeckel.

Definition.—Surface of the shell armed with radial spines.

4. Spongodruppa frangula, n. sp.

Cortical shell one and a third times as long as broad, three times as broad as the spherical medullary shell. Spongy framework loose, with large meshes, its thickness half as large as the diameter of the medullary shell. Surface covered with numerous (forty to fifty) thin, bristle-shaped, radial spines, about as long as the cortical shell.

Dimensions.—Length of the cortical shell 0.24, breadth 0.18; thickness of its wall 0.035; diameter of the medullary shell 0.06.

Habitat.—North Pacific, Station 244, depth 2900 fathoms.

5. Spongodruppa elliptica, Haeckel.

Acanthosphæra elliptica, Ehrenberg, 1872, Abhandl. d. k. Akad. d. Wiss. Berlin, p. 285, Taf. vii. fig. 4.

Cortical shell nearly twice as long as broad, four times as broad as the ellipsoidal medullary shell. Spongy framework compact, with small meshes. Surface covered with very numerous short radial spines, about as long as the medullary shell.

Dimensions.—Length of the cortical shell 0.2, breadth 0.11; length of the medullary shell 0.04, breadth 0.03.

Habitat.—Philippine Sea, Ehrenberg, Station 206, depth 2100 fathoms.

6. Spongodruppa polyacantha, Haeckel.

Haliomma polyacanthum, J. Müller, 1858, Abhandl., p. 36, Taf. i. figs. 10, 11. Haliomma polyacanthum, Haeckel, 1862, Monogr. d. Radiol., p. 430.

Cortical shell one and a third times as long as broad, twice as broad as the ellipsoidal medullary shell. Spongy framework loose on the surface, with large regular meshes. Surface covered with fifteen to twenty thick, conical spines, about as long as the radius of the shell.

Dimensions.—Length of the cortical shell 0.12, of the medullary shell 0.09; diameter of the medullary shell 0.05 to 0.06.

Habitat.—Mediterranean (south coast of France); Atlantic (Canary Islands), Station 354, surface.

Genus 149. Spongatractus,^[28] n. gen.

Definition.—Spongurida with spongy ellipsoidal cortical shell, enclosing a simple, spherical or ellipsoidal, latticed medullary shell. On the poles of the axis occur two opposite strong spines.

The genus Spongatractus differs from Spongodruppa by development of two strong spines in the axis of the shell, on its two opposite poles; therefore it bears the same relation to the latter that Lithatractus does to Druppula, and can be derived from Lithatractus by a spongy thickening of the cortical shell.

1. Spongatractus pachystylus, Haeckel.

Spongosphæra pachystyla, Ehrenberg, 1875, Abhandl. d. k. Akad. d. Wiss. Berlin, p. 82, Taf. xxvi. fig. 3.

Cortical shell one and a half times as long as broad, with rough surface. Spongy framework compact, with small meshes, about as thick as the spherical medullary shell. Polar spines very stout, conical, slightly sulcated, about as long as the breadth of the cortical shell, as broad at the base as the medullary shell.

Dimensions.—Length of the cortical shell 0.2, breadth 0.13; thickness of the spongy wall 0.045; diameter of the medullary shell 0.04.

Habitat.—Fossil in the rocks of Barbados, Ehrenberg; living in the Equatorial Atlantic, Station 348, depth (2450) fathoms.

2. Spongatractus fusiformis, n. sp.

Cortical shell one and a third times as long as broad, with nearly smooth surface. Spongy framework very compact, with very small meshes, about as thick as the radius of the spherical medullary shell. Polar spines very strong, three-sided pyramidal, about as long as the breadth of the cortical shell, as broad at the base as the medullary shell.

Dimensions.—Length of the cortical shell 0.16 to 0.18, breadth 0.12 to 0.14; thickness of the spongy wall 0.02; diameter of the medullary shell 0.04.

Habitat.—Pacific, central area, Station 268, depth 2900 fathoms.

3. Spongatractus streptacanthus, n. sp.

Cortical shell twice as long as broad, with thorny surface. Spongy framework loose, with large meshes, about as thick as the ellipsoidal medullary shell. Polar spines very long, three-sided prismatic, with three spirally contorted edges, much longer than the cortical shell, half as broad as the medullary shell.

Dimensions.—Length of the cortical shell 0.25, breadth 0.13; thickness of the spongy wall 0.03; diameter of the medullary shell 0.03 to 0.04.

Habitat.—North Atlantic, off Canary Islands, Haeckel.

Genus 150. Spongoliva,^[29] n. gen.

Definition.—Spongurida with spongy ellipsoidal cortical shell, enclosing a double, spherical or ellipsoidal, latticed medullary shell. Polar spines absent.

The genus Spongoliva differs from the nearest Spongodruppa by duplication of the medullary shell; it bears therefore the same relation to this that Prunulum does to Druppula, and can be regarded as a Prunulum, in which the simple latticed cortical shell is replaced by a spongy framework.

Subgenus 1. Spongolivetta, Haeckel.

Definition.—Surface of the shell smooth or rough, without radial spines.

1. Spongoliva cerasina, n. sp.

Cortical shell one and a fourth times as long as broad, with smooth surface, four times as broad as the outer spherical medullary shell. Spongy framework very compact, with very small meshes, its thickness equal to the diameter of the outer medullary shell.

Dimensions.—Length of the cortical shell 0.2, breadth 0.16; thickness of its wall 0.04; diameter of the outer medullary shell 0.04, of the inner 0.014.

Habitat.—Fossil in the rocks of Barbados.

2. Spongoliva prunulina, n. sp.

Cortical shell one and a third times as long as broad, with smooth surface, three times as large as the outer ellipsoidal medullary shell. Spongy framework very compact, with small meshes, its thickness equal to the diameter of the inner medullary shell.

Dimensions.—Length of the cortical shell 0.24, breadth 0.18; thickness of its wall 0.03; size of the outer medullary shell 0.08 to 0.06, of the inner 0.03.

Habitat.—Pacific, central area, Station 265, depth 2900 fathoms.

3. Spongoliva persicina, n. sp.

Cortical shell one and a half times as long as broad, with rough surface, five to six times as large as the ellipsoidal outer medullary shell. Spongy framework loose, with large meshes, its thickness about equal to the outer medullary shell.

Dimensions.—Length of the cortical shell 0.26, breadth 0.18; thickness of its wall 0.04; size of the outer medullary shell 0.045 to 0.035, of the inner 0.015.

Habitat.—Equatorial Atlantic, Station 348, depth (2450) fathoms.

4. Spongoliva amygdalina, n. sp.

Cortical shell twice as long as broad, with thorny surface, ten times as long as the small spherical outer medullary shell. Spongy framework loose, with large meshes, its thickness one and a half times as large as the outer medullary shell.

Dimensions.—Length of the cortical shell 0.3, breadth 0.16; thickness of its wall 0.045; size of the outer medullary shell 0.03, of the inner 0.015.

Habitat.—Fossil in the Tertiary rocks of Sicily (Caltanisetta).

Subgenus 2. Spongolivina, Haeckel.

Definition.—Surface of the shell armed with radial spines.

5. Spongoliva opuntina, n. sp.

Cortical shell one and a third times as long as broad, armed with numerous thin, bristle-shaped, radial spines, nearly as long as the shell. Spongy framework loose, with large meshes, its thickness nearly equal to the diameter of the outer spherical medullary shell.

Dimensions.—Length of the cortical shell 0.18, breadth 0.14; thickness of its wall 0.035; diameter of the outer medullary shell 0.04, of the inner 0.02.

Habitat.—South Atlantic, Station 325, surface.

6. Spongoliva daturina, n. sp.

Cortical shell one and a half times as long as broad, armed with numerous, thick and short, conical radial spines, about as long as the outer medullary shell. Spongy framework compact, with small meshes, its thickness equal to half the length of the outer ellipsoidal medullary shell.

Dimensions.—Length of the cortical shell 0.24, breadth 0.16; thickness of its wall 0.025; diameter of the outer medullary shell 0.045 to 0.035, of the inner 0.025.

Habitat.—Pacific, central area, Station 272, surface.

Genus 151. Spongoxiphus,^[30] n. gen.

Definition.—Spongurida with spongy ellipsoidal cortical shell, enclosing a double, spherical or ellipsoidal, latticed medullary shell. On the poles of the axis occur two opposite strong spines.

The genus Spongoxiphus differs from Spongoliva by the development of two strong spines in the axis of the shell, on its two opposite poles. From the similar Spongatractus it differs in the duplication of the medullary shell. It may also be regarded as a Stylatractus, in which the simple latticed cortical shell is replaced by an irregular spongy framework.

1. Spongoxiphus sphærococcus, n. sp.

Cortical shell one and a half times as long as broad, with thorny surface. Spongy framework compact, with small meshes, its thickness equal to the radius of the outer medullary shell. Both medullary shells spherical, the outer three times as broad as the inner. Polar spines very stout, conical, slightly sulcated, about half as long as the cortical shell, as broad at the base as the outer medullary shell. (Differs from Spongatractus pachystylus almost only in the double medullary shell.)

Dimensions.—Length of the cortical shell 0.18, breadth 0.12; thickness of the spongy wall 0.025; diameter of the outer medullary shell 0.05, of the inner 0.016.

Habitat.—Fossil in the rocks of Barbados (Haeckel); also living in the Pacific, central area, Station 265, depth 2900 fathoms.

2. Spongoxiphus prunococcus, n. sp. (Pl. 17, figs. 12, 13).

Spongostylus prunococcus, Haeckel, 1881, Prodromus, p. 455, et Atlas, pl. xvii. figs. 12, 13.

Cortical shell one and a third times as long as broad, with smooth surface. Spongy framework very compact, with very small meshes, its thickness about equals the breadth of the outer medullary shell. Both medullary shells ellipsoidal, the outer three times as large as the inner. Polar spines very stout, three-sided pyramidal, about half as long as the cortical shell, on the base about as broad as the outer medullary shell. (Differs from the preceding in the ellipsoidal form of both medullary shells, and in the finer structure of the spongy framework.)

Dimensions.—Length of the cortical shell 0.18 to 0.2, breadth 0.14 to 0.16; thickness of the spongy wall 0.035 to 0.04; length of the outer medullary shell 0.04 to 0.06, breadth 0.03 to 0.04.

Habitat.—Pacific, central area, Stations 265 to 268, depths 2700 to 2900 fathoms.

Family XIV. Artiscida, Haeckel (Pl. 39, figs. 9, 10; Pl. 48, fig. 5).

Artiscida, Haeckel, 1881, Prodromus, p. 462.

Definition.—Prunoidea with an ellipsoidal twin-shell divided by an equatorial stricture into two communicating hemiellipsoidal or hemispherical chambers, without enclosed medullary shell. Central capsule ellipsoidal, with or without equatorial stricture.

The family Artiscida has a simple fenestrated outer shell, like that of the Ellipsida, but differs from these in the presence of an equatorial constriction, by which it assumes a characteristic twin form, somewhat similar to a violin (Pl. 39, figs. 9, 10). From the Cyphinida, which have the same form of the cortical shell, the Artiscida differ in the absence of the medullary shell. It is possible that the Artiscida are descended from the Cyphinida (by loss of the medullary shell), but it is more probable that they arise from the Ellipsida by an annular constriction in the equatorial plane (perhaps the formation of the shell originally took place while the central capsule was undergoing division). Both halves of the twin shell are always of the same size and form. Its outer surface is either smooth or covered with radial spines (Artiscus, Pl. 39, fig. 9). Sometimes on the opposite poles of the main axis are developed solid spines (Stylartus, Pl. 48, fig. 5) or hollow fenestrated tubes (Cannartus, Pl. 39, fig. 10).

The Central Capsule is either simply ellipsoidal, or has also an equatorial constriction, which divides it into two equal halves. It is constantly smaller than the surrounding shell, and separated from its inner surface by a thicker or thinner jelly-mantle, the calymma.

Synopsis of the Genera of Artiscida.

On the poles of the main axis neither solid spines nor hollow tubes,	152. Artiscus.
On the poles of the main axis two solid spines (or bunches of spines),	153. Stylartus.
On the poles of the main axis two hollow fenestrated tubes,	154. Cannartus.

Genus 152. Artiscus,^[31] Haeckel, 1881, Prodromus, p. 462.

Definition.—Artiscida without peculiar polar appendages (without strong solid spines or hollow fenestrated tubes on the poles of the main axis).

The genus Artiscus represents the most simple and primitive form of the Artiscida, and may therefore be regarded as the ancestral form of this subfamily. It resembles an ordinary double loaf, composed of two equal, nearly ellipsoidal fenestrated shells separated by the stricture in the equatorial plane. Artiscus can be derived from Cenellipsis simply by this equatorial constriction. But it can also be derived from Cyphanta by loss of the medullary shell.

Subgenus 1. Artiscium, Haeckel.

Definition.—Surface of the shell smooth or rough, without radial rods or spines.

1. Artiscus paniscus, n. sp.

Pores of the shell regular, hexagonal, four times as broad as the bars; ten to twelve pores on the half meridian, eight to nine on the half equator. Surface smooth. (The network of this species is quite the same as that of the proximal cameræ of Panartus diploconus, Pl. 40, fig. 1.)

Dimensions.—Main axis of the shell 0.12, equatorial axis 0.07; meshes 0.013, bars 0.003.

Habitat.—Pacific, central area, Station 271, depth 2425.

2. Artiscus facetus, n. sp.

Pores of the shell regular, circular, with prominent hexagonal frame, twice as broad as the bars; twenty-two to twenty-four pores on the half meridian, fourteen to fifteen on the half equator. Surface a little thorny. (The shell of this species exhibits nearly the same formation as that of Cyphonium virgineum, Pl. 39, fig. 12, but without enclosed medullary shells.)

Dimensions.—Main axis of the shell 0.15, equatorial axis 0.09; meshes 0.01, bars 0.005.

Habitat.—Pacific, central area, Station 266, depth 2750 fathoms.

3. Artiscus paniculus, n. sp.

Pores of the shell regular, circular, without hexagonal frame, as broad as the bars; fourteen to sixteen pores on the half meridian, ten to eleven on the half equator. Surface quite smooth.

Dimensions.—Main axis of the shell 0.13, equatorial axis 0.06; meshes 0.01, bars 0.01.

Habitat.—Fossil in the Tertiary rocks of Barbados (Haeckel).

4. Artiscus panarius, n. sp.

Pores of the shell irregular, roundish, twice to four times as broad as the bars; sixteen to eighteen pores on the half meridian, twelve to thirteen on the half equator. Surface smooth.

Dimensions.—Main axis of the shell 0.11, equatorial axis 0.06; meshes 0.005 to 0.02, bars 0.001 to 0.004.

Habitat.—Western Tropical Pacific, Station 224, depth 1850 fathoms.

Subgenus 2. Artidium, Haeckel, 1881, Prodromus, p. 462.

Definition.—Surface of the shell covered with radial rods or spines.

5. Artiscus elegans, n. sp.

Pores of the shell regular, circular, with hexagonal frames, twice as broad as the bars; fourteen pores on the half meridian, eight to nine on the half equator. From every corner of the hexagonal frames (between every three pores) starts a thin, three-sided pyramidal spine, twice as large as a pore.

Dimensions.—Main axis 0.13, equatorial axis 0.08; meshes 0.007, bars 0.004; spines 0.015 long.

Habitat.—South Atlantic, Station 332, depth 2200 fathoms.

6. Artiscus nodosus, n. sp. (Pl. 39, fig. 9).

Pores of the shell subregular, circular, without hexagonal frame, three times as broad as the bars; sixteen to eighteen on the half meridian, ten to twelve on the half equator. Irregularly scattered on the whole surface a variable number (twenty-five to thirty in all) of stout short radial spines or rather blunt rods; the length and thickness of these is the same, and equals the size of two to three meshes; its form resembles a truncated six-sided pyramid.

Dimensions.—Main axis 0.11, equatorial axis 0.08; meshes 0.01, bars 0.003; length and thickness of the radial sticks 0.02.

Habitat.—Pacific, central area, Station 272, depth 2600 fathoms.

7. Artiscus hystrix, n. sp.

Pores of the shell irregular, roundish, of very unequal size and dissimilar form, twice to eight times as broad as the bars; ten to fifteen on the half meridian, seven to nine on the half equator. Irregularly scattered on the whole surface a large number of thin conical spines, about as large as the meshes, partly directed radially, partly obliquely. (The shell of this species resembles very much that of Cyphonium ceratospyris (p. 366) = Didymocyrtis ceratospyris, Monogr. d. Radiol., 1862, Taf. xxii. fig. 14, but is without the enclosed inner shells.)

Dimensions.—Main axis 0.12, equatorial axis 0.07; meshes 0.004 to 0.02, bars 0.002 to 0.005; spines 0.01 to 0.02.

Habitat.—Atlantic, Eastern Tropical part, Station 346, surface.

Genus 153. Stylartus,^[32] Haeckel, 1881, Prodromus, p. 462.

Definition.—Artiscida with two strong, solid, polar spines, or two bunches of polar spines, opposite on the two poles of the main axis.

The genus Stylartus differs from Artiscus by the production of two large opposite spines in the main axis, starting from both poles of it; sometimes every spine is surrounded by a group of smaller radial spines. The genus is nearly allied to Ellipsoxiphus (p. 295), and differs from it only in the equatorial stricture of the ellipsoidal shell. But it may also be derived from the similar Cyphinus (Pl. 39, fig. 14) by loss of the medullary shell.

Subgenus 1. Stylartella, Haeckel.

Definition.—On each pole of the main axis only one single large spine.

1. Stylartus bipolaris, n. sp. (Pl. 48, fig. 5).

Shell thick walled, rough; both its chambers nearly spherical, with irregular, roundish pores, twice to four times as broad as the bars; eight to ten on the half equator of each chamber. Polar spines very strong, conical, as long as the greatest breadth.

Dimensions.—Length of the shell (without spines) 0.18, greatest breadth 0.13; length of the polar spines 0.13, basal breadth 0.03.

Habitat.—Western Tropical Pacific, Station 224, depth 1850 fathoms.

2. Stylartus bicuspis, n. sp.

Shell thin walled, smooth, with regular, circular pores, twice as broad as the bars; twelve to fourteen on the half equator of each chamber. Polar spines very stout, straight, three-sided pyramidal, half as long as the shell.

Dimensions.—Length of the shell 0.16, greatest breadth 0.12; length of the polar spines 0.08, basal thickness 0.025.

Habitat.—Pacific, central area. Station 266, depth 2750 fathoms.

Subgenus 2. Stylartura, Haeckel.

Definition.—On each pole of the main axis a bunch of several spines.

3. Stylartus palatus, n. sp.

Shell thick walled, thorny, with irregular, roundish pores, twice to three times as broad as the bars; fifteen to eighteen on the half equator of each chamber. On each pole of the main axis a large conical spine, surrounded by a group of ten to fifteen smaller spines, one-third to two-thirds as long as the breadth of the deep equatorial stricture.

Dimensions.—Length of the shell 0.14, greatest breadth 0.09; length of the polar spines 0.03 to 0.06, basal breadth 0.005 to 0.015.

Habitat.—Indian Ocean, Madagascar, Rabbe, surface.

4. Stylartus penicillus, n. sp.

Shell thin walled, smooth, with irregular, roundish pores, three to four times as broad as the bars; ten to twelve on the half equator of each chamber. On each pole of the main axis a brush-like bunch of twenty to thirty thin conical radial spines, half as long as the shell.

Dimensions.—Length of the shell 0.15, greatest breadth 0.1; length of the polar spines 0.08, basal breadth 0.005.

Habitat.—Equatorial Atlantic, Station 347, surface.

Genus 154. Cannartus,^[33] Haeckel, 1881, Prodromus, p. 462.

Definition.—Artiscida with two hollow polar tubes (fenestrated cylindrical or conical tubuli, opposite on the two poles of the main axis).

The genus Cannartus differs from Artiscus by the production of two opposite hollow tubes on both poles of the main axis. The cavity of the conical or cylindrical fenestrated tubes communicates freely with that of the shell; the network in both is the same. The distal end of the tubes is nearly always broken off, sometimes closed, with a conical apex. Cannartus can be derived either from Pipettella by a transverse equatorial constriction, or from Cannartiscus by the loss of the medullary shell, or from Artiscus by the production of the polar tubes.

1. Cannartus violina, n. sp. (Pl. 39, fig. 10).

Pores of the shell subregular, circular, twice to three times as broad as the bars; eighteen to twenty on the half meridian, fourteen to sixteen on the half equator. Shell-wall in the "tropical zone" of both halves thickened. Polar tubes nearly cylindrical, about as long as the main axis, distal ends broken off.

Dimensions.—Main axis 0.14, equatorial axis 0.09; meshes 0.008, bars 0.003; length of the polar tubes 0.12, breadth 0.02 to 0.03.

Habitat.—Pacific, central area, Station 268, depth 2900 fathoms.

2. Cannartus bitubulus, n. sp.

Pores of the shell regular, circular, hexagonally framed, of the same breadth as the bars; fourteen to sixteen on the half meridian, ten to twelve on the half equator. Polar tubes cylindrical, longer than the main axis, sulcated, distal ends broken off. (Similar to Pipetta tuba, Pl. 39, fig. 7, but with equatorial stricture and without medullary shell.)

Dimensions.—Main axis 0.16, equatorial axis 0.12; meshes and bars 0.006; length of the polar tubes 0.2, breadth 0.025.

Habitat.—South Atlantic, Station 332, depth 2200 fathoms.

3. Cannartus biscottus, n. sp.

Pores of the shell irregular, roundish, twice to three times as broad as the bars; ten to twelve on the half meridian, six to eight on the half equator. Polar tubes conical, shorter than the main axis, with closed apex. (Similar to Cannartidium bicinctum, Pl. 39, fig. 18, but without enclosed medullary shell.)

Dimensions.—Main axis 0.11, equatorial axis 0.07; meshes 0.005 to 0.01, bars 0.003; length of the polar tubes 0.08, breadth on the base 0.03.

Habitat.—Equatorial Atlantic, Station 348, depth 2450 fathoms.

Family XV. Cyphinida, Haeckel (Pl. 39, figs. 11-19).

Cyphinida, Haeckel, 1881, Prodromus, p. 462.

Definition.—Prunoidea with ellipsoidal twin-shell, divided by an equatorial stricture into two communicating hemiellipsoidal or hemispherical chambers; this external twin-shell (cortical shell) is either simple or double, and encloses one or more internal concentric shells (medullary shells). Central capsule ellipsoidal, commonly with an equatorial constriction.

The family Cyphinida have the same characteristic twin-form of the cortical shell as the Artiscida, but differ from them in the presence of a simple or double internal medullary shell, connected with the cortical shell by radial beams. The fenestrated shell is therefore composed of two or more concentric shells as in the Druppulida, but differs from these in the ring-like equatorial constriction.

The Medullary Shell, in the middle of the central capsule, is either single or double, composed of two concentric shells. As in the Druppulida, the form of the medullary shells is either spherical (Pl. 39, fig. 12a) or lenticular, compressed from both poles of the main axis (Pl. 39, fig. 18a); sometimes the inner medullary shell is spherical, the outer lenticular.

The Radial Beams, which connect the medullary shell with the equatorial constriction of the cortical shell, lie either all in the equatorial plane (Pl. 39, fig. 11) or near it on both sides (Pl. 39, figs. 12a, 18a).

The Cortical Shell is commonly simple (Pl. 39, figs. 12, 18), sometimes composed of two concentric shells (Pl. 39, fig. 13), rarely of three. As in the Artiscida, also in the Cyphinida, from both poles of the main axis solid spines or hollow fenestrated tubes are often developed (Pl. 39, figs. 14, 16-18).

The Central Capsule of the Cyphinida (Pl. 39, fig. 13) is of the same form as in the Artiscida, generally ellipsoidal, but with an equatorial ring-like stricture, which divides it into two equal halves. It encloses the simple or double medullary shell, and is perforated by the radial beams starting from this. From the inner surface of the surrounding cortical shell it is separated by a thicker or thinner jelly-layer, the calymma. (Compare also Taf. xxii. fig. 14 of my Monograph, 1862.)

Synopsis of the Genera of Cyphinida.

Cortical shell without peculiar spines or hollow fenestrated tubes on both poles of the main axis.	$\scriptstyle {\left\{{\begin{matrix}\ \\\\\ \\\ \\\ \ \end{matrix}}\right.}$	Cortical twin-shell simple	$\scriptstyle {\left\{{\begin{matrix}\ \\\ \end{matrix}}\right.}$	Medullary shell simple,	155. Cyphanta.
				Medullary shell double,	156. Cyphonium.
		Cortical twin-shell double or triple; medullary shell double.	$\scriptstyle {\left\{{\begin{matrix}\ \\\ \end{matrix}}\right.}$	Cortical shell double,	157. Cypassis.
				Cortical shell triple,	158. Cyphocolpus.
Cortical shell simple, with peculiar spines or hollow fenestrated tubes on both poles of the main axis.	$\scriptstyle {\left\{{\begin{matrix}\ \\\\\ \\\ \\\ \ \end{matrix}}\right.}$	Two opposite polar spines (or bunches of spines).	$\scriptstyle {\left\{{\begin{matrix}\ \\\ \end{matrix}}\right.}$	Medullary shell simple,	159. Cyphinus.
				Medullary shell double,	160. Cyphinidium.
		Two opposite hollow fenestrated polar tubes.	$\scriptstyle {\left\{{\begin{matrix}\ \\\ \end{matrix}}\right.}$	Medullary shell simple,	161. Cannartiscus.
				Medullary shell double,	162. Cannartidium.

Genus 155. Cyphanta,^[34] n. gen.

Definition.—Cyphinida with simple cortical shell and simple medullary shell, without polar spines or tubes.

The genus Cyphanta is the most simple of all Cyphinida, and can be regarded as the common ancestral form of this family. It may be derived phylogenetically from Druppula by a ring-like constriction in the equatorial plane of the ellipsoidal cortical shell, or from Artiscus by secondary formation of a central (spherical or ellipsoidal) medullary shell.

Subgenus 1. Cyphantella, Haeckel.

Definition.—Surface of the cortical shell smooth, without spines or thorns.

1. Cyphanta colpodes, n. sp.

Cortical shell thin walled, with smooth surface; its pores regular, hexagonal, three to four times as broad as the bars; ten to twelve on the half meridian, seven to eight on the half equator. Medullary shell spherical, its diameter one-third of the equatorial axis of the cortical shell. (The cortical shell of this species is nearly identical with the central half of the cortical shell of Panartus diploconus, Pl. 40, fig. 1.)

Dimensions.—Main axis of the cortical shell 0.12, equatorial axis 0.07; meshes 0.013; bars 0.003; diameter of the medullary shell 0.025.

Habitat.—South Pacific, Station 285, depth 2375 fathoms.

2. Cyphanta circopora, n. sp.

Cortical shell thick walled, with smooth surface; pores subregular, circular, twice as broad as the bars; eighteen to twenty on the half meridian, twelve to fourteen on the half equator. Medullary shell spherical, its diameter one-half of the equatorial axis of the cortical shell. (The shell of this species is very similar to that of Cannartiscus amphiconiscus, Pl. 39, fig. 19, but without the polar tubes of that species.)

Dimensions.—Main axis of the cortical shell 0.13, equatorial axis 0.08; meshes 0.007, bars 0.003; diameter of the medullary shell 0.04.

Habitat.—Pacific, central area. Station 266, depth 2750 fathoms.

3. Cyphanta lævis, Haeckel.

Ommatospyris lævis, Ehrenberg, 1872, Monatsber. d. k. preuss. Akad. d. Wiss. Berlin, p. 318.

Cortical shell thin walled, with smooth surface; pores of it irregular, roundish, of very different size (some very large in the tropical circles of both hemispheres). Pores twice to six times as broad as the bars; ten to twelve on the half meridian, six to eight on the half equator. Medullary shell spheroidal, compressed, its main axis somewhat shorter than its equatorial axis, which attains half the length of that of the cortical shell. (This species may be perhaps identical with Ommatospyris lævis of Ehrenberg, the diagnosis of which is insufficient and figure not given.)

Dimensions.—Main axis of the cortical shell 0.1, equatorial axis 0.06; meshes 0.005 to 0.02, bars 0.002 to 0.04; diameter of the medullary shell 0.03.

Habitat.—Philippine Sea (Ehrenberg), Station 213, depths 2650 and 3300 fathoms.

4. Cyphanta arachnoides, n. sp.

Cortical shell very delicate and thin walled, cobweb-like, with smooth surface; pores irregular, polygonal (mostly pentagonal or hexagonal), eight to ten times as broad as the thread-like bars; ten to twelve on the half meridian, six to eight on the half equator. Medullary shell spheroidal, compressed, its main axis shorter than its equatorial axis, which is about one-third that of the cortical shell. (This species is very similar to the middle part of the shell of Ommatocampe profundissima, Ehrenberg, 1872, Abhandl. d. k. Akad. d. Wiss. Berlin, Taf. viii. fig. 6.)

Dimensions.—Main axis of the cortical shell 0.11, equatorial axis 0.06; meshes 0.01 to 0.02, bars 0.002; diameter of the medullary shell 0.02.

Habitat.—Atlantic, Canary Islands (Lanzerote), surface.

Subgenus 2. Cyphantissa, Haeckel.

Definition.—Surface of the cortical shell spiny, everywhere scattered with numerous thorns or spines.

5. Cyphanta hispida, n. sp.

Cortical shell thick walled, with spiny surface; pores regular, circular, with hexagonal frame, twice as broad as the bars; twelve to fourteen on the half meridian, eight to ten on the half equator. From the corners of the hexagonal frames (between every three pores) arise short, straight, conical radial spines, somewhat longer than the breadth of the pores. Medullary shell subspherical, its diameter about one-third of the equatorial axis of the cortical shell. (The appearance of the cortical shell is the same as that of the middle part of Peripanartus amphiconus, Pl. 40, fig. 5.)

Dimensions.—Main axis of the cortical shell 0.12, equatorial axis 0.07; meshes 0.01, bars 0.005; length of the spines 0.012; diameter of the medullary shell 0.02.

Habitat.—Pacific, central area, Station 274, depth 2750 fathoms.

6. Cyphanta hystrix, n. sp.

Cortical shell thin walled, with thorny surface; pores irregular, roundish, of very unequal size, twice to six times as broad as the bars; twelve to eighteen on the half meridian, eight to thirteen on the half equator. Between the pores irregularly scattered, bristle-like, thin spines about the same size, partly straight, partly oblique, rising from the surface. Medullary shell lenticular, compressed, its equatorial axis one and a half times the length of the main axis, and about half that of the cortical shell.

Dimensions.—Main axis of the cortical shell 0.15, equatorial axis 0.09; meshes 0.004 to 0.02, bars 0.003 to 0.006; length of the spines 0.02; diameter of the medullary shell 0.04.

Habitat.—South Atlantic, Station 318, surface.

Genus 156. Cyphonium,^[35] n. gen.

Definition.—Cyphinida with simple cortical shell and double medullary shell, without polar spines or tubes.

The genus Cyphonium contains a number of very common species, among which are the earliest known forms of this family, partly described by Ehrenberg as Ommatospyris (which genus contains also a number of other Prunoidea), partly by me (1862) as Didymocyrtis. Both names are inadequate, as allusions to quite different families of Nassellaria, but may be retained as significations of subgeneric divisions. Cyphonium differs from Cyphanta by the double medullary shell, which is either spherical or lenticular.

Subgenus 1. Ommatospyris, Ehrenberg (partim).

Definition.—Surface of the cortical shell smooth, without thorns or spines.

1. Cyphonium coscinoides, n. sp.

Ommatospyris coscinoides, Haeckel, 1881, Prodromus, p. 462.

Cortical shell thin walled, with smooth surface; pores regular, hexagonal, three to four times as broad as the bars; five to six on the half meridian, eight to nine on the half equator of each chamber. Medullary shells both spherical. (The cortical shell of this species is nearly the same as that of Cyphanta colpodes, and as the middle part of the cortical shell of Panartus diploconus, Pl. 40, fig. 1.)

Dimensions.—Main axis of the cortical shell 0.11, equatorial axis 0.06; greatest breadth of the chambers 0.08; pores 0.013, bars 0.003.

Habitat.—North Pacific, Station 244, surface.

2. Cyphonium virgineum, n. sp. (Pl. 39, figs. 12, 12a).

Ommatospyris virginea, Haeckel, 1881, Prodromus et Atlas (pl. xxxix. fig. 12a).

Cortical shell thick walled, with smooth surface (sometimes a little rough with very small thorns); pores subregular, circular, with hexagonal elevated frames, about as broad as the bars; ten to twelve on the half meridian, sixteen to eighteen on the half equator of each chamber. Medullary shells (fig. 12a) both spherical. (Sometimes, as in the figured specimen, the shell is somewhat irregular, an individual abnormality.)

Dimensions.—Main axis of the cortical shell 0.13 to 0.15; equatorial axis of the structure 0.08 to 0.09, of each chamber 0.1 to 0.12, pores and bars 0.005 to 0.007.

Habitat.—Pacific, western tropical part, Station 225, depth 4475 fathoms.

3. Cyphonium ethmarium, n. sp.

Ommatospyris ethmaria, Haeckel, 1881, Prodromus, p. 462.

Cortical shell thin walled, with quite smooth surface; pores subregular, circular (without hexagonal frame), twice as broad as the bars; nine to ten on the half meridian of each chamber, sixteen to eighteen on its half equator. Medullary shells both spherical. (This species resembles the proximal internal chambers of Peripanartus atractus, Pl. 40, fig. 7.)

Dimensions.—Main axis 0.13, equatorial axis 0.07; greatest breadth 0.09; pores 0.006, bars 0.003.

Habitat.—Equatorial Atlantic, Station 347, surface.

4. Cyphonium trinacrium, n. sp.

Cortical shell thick walled, with rough surface; pores subregular, circular (without hexagonal frame), not broader than the bars; five to six on the half meridian of each chamber, nine to ten on its half equator. Medullary shells both compressed, lenticular. This species resembles Cypassis entomocora vel Ommatocampe trinacria, Stöhr, 1880, loc. cit., p. 90, Taf. ii. fig. 1, but has not its external mantle. It may be the ancestral form of it (both in an ontogenetic and phylogenetic sense).

Dimensions.—Main axis 0.11, equatorial axis 0.07; greatest breadth 0.08; pores 0.005, bars 0.005.

Habitat.—Fossil in Tertiary rocks of Sicily, Caltanisetta, Haeckel (Grotte, Stöhr?).

5. Cyphonium diattus, n. sp.

Cortical shell thin walled, with quite smooth surface; pores irregular, polygonal, mostly pentagonal or hexagonal, three to six times as broad as the bars; six to seven on the half meridian of the chamber, ten to twelve on its half equator. Medullary shells both spherical. (Resembles Cyphonium profundum, Ehrenberg, 1872, loc. cit., Taf. x. fig. 5, but does not possess the spines of the surface.)

Dimensions.—Main axis 0.13, equatorial axis 0.06; greatest breadth 0.08; pores 0.005 to 0.012, bars 0.002 to 0.004.

Habitat.—Indian Ocean, western part (Zanzibar), Pullen, depth 2200 fathoms.

6. Cyphonium mammarium, n. sp.

Cortical shell thick walled, with smooth surface (sometimes a little rough); pores irregular, roundish, twice to three times as broad as the bars; eleven to twelve on the half meridian of each chamber, sixteen to nineteen on its half equator. Internal medullary shell spherical, external lenticular compressed, sometimes both spherical or both compressed. (Resembles the internal cortical twin-shell of Cyphocolpus virginis, Pl. 40, fig. 11.)

Dimensions.—Main axis 0.14, equatorial axis 0.08, greatest breadth 0.09; pores 0.004 to 0.006, bars 0.002.

Habitat.—South Pacific, Station 285, depth 2375 fathoms.

Subgenus 2. Ommatocyrtis, Haeckel.

Definition.—Surface of the cortical shell thorny or spiny.

7. Cyphonium hexagonium, n. sp.

Didymocyrtis hexagonia, Haeckel, 1881, Prodromus.

Cortical shell thin walled, with spiny surface; pores regular or subregular, hexagonal, twice to three times as broad as the bars; five to six on the half meridian, nine to ten on the half equator of each chamber. Radial spines between them conical, about as long as the pores. Medullary shells both spherical.

Dimensions.—Main axis 0.14, equatorial axis 0.08; greatest breadth of each chamber 0.1; pores 0.012, bars 0.004.

Habitat.—Pacific, central area, Station 268, depth 2900 fathoms.

8. Cyphonium facettarium, n. sp.

Didymocyrtis facettaria Haeckel, 1881, Prodromus.

Cortical shell thick walled, with spiny surface; pores subregular, circular, with elevated hexagonal frames, twice as broad as the bars; eight to nine on the half meridian, fourteen to sixteen on the half equator of each chamber. In the corners of the hexagons (between every three meshes) arise radial spines, about twice as long as the pores. Both medullary shells spheroidal compressed. (This species is nearly identical with the internal cortical twin-shell of Peripanartus amphiconiscus, Pl. 40, fig. 5.)

Dimensions.—Main axis 0.12, equatorial axis 0.07; greatest breadth of both chambers 0.09; pores 0.01, bars 0.005, spines 0.02.

Habitat.—Western Tropical Pacific, Station 225, depth 4475 fathoms.

9. Cyphonium cribellum, n. sp. (Pl. 39, fig. 11).

Cortical shell thick walled, with spiny surface; pores regular, circular, about as broad as the bars; seven to eight on the half meridian of each chamber, thirteen to fifteen on its half equator. Radial spines between them conical, twice as long as the pores. Medullary shells both lenticular.

Dimensions.—Main axis 0.11, equatorial axis 0.06; greatest breadth 0.08; pores and bars 0.004.

Habitat.—North Atlantic, Station 353, surface.

10. Cyphonium profundum, Haeckel.

Ommatospyris profunda, Ehrenberg, 1872, Abhandl. d. k. Akad. d. Wiss. Berlin, p. 297, Taf. viii. fig. 5, Taf. x. fig. 5.

Cortical shell thin walled, with thorny surface; pores irregular, polygonal, three to six times as broad as the thin bars; five to six on the half meridian of each chamber, ten to twelve on its half equator. Thorns of the surface short. Medullary shells both spherical.

Dimensions.—Main axis 0.1, equatorial axis 0.06; greatest breadth 0.07; pores 0.005 to 0.012, bars 0.002, spines 0.005.

Habitat.—Pacific, tropical zone; Philippine Sea, depth 3300 fathoms, Ehrenberg; Stations 266 to 274, depth 2350 to 2925 fathoms.

11. Cyphonium ceratospyris, Haeckel.

Didymocyrtis ceratospyris, Haeckel, 1862, Monogr. d. Radiol., p. 445, pl. xxii. figs. 14-16. Haliomma didymocyrtis, Haeckel, 1860, Monatsber. d. k. preuss. Akad. d. Wiss. Berlin, p. 816.

Cortical shell thin walled, with spiny surface; pores irregular, roundish, three to nine times as broad as the bars; five to six on the half meridian of each chamber, eight to nine on its half equator. Spines of the surface partly very short, partly as long as the largest pores, either radially or obliquely inserted. Medullary shells both spherical. (Compare the detailed description and figures also of the soft body in my Monograph, loc. cit.)

Dimensions.—Main axis of the cortical shell 0.12, equatorial axis (in the stricture) 0.06; greatest breadth 0.08; pores 0.03 to 0.2, bars 0.002 to 0.006, spines 0.05 to 0.015.

Habitat.—Mediterranean (Messina), Canary Islands (Lanzerote), Haeckel.

Genus 157. Cypassis,^[36] n. gen.

Definition.—Cyphinida with double cortical shell and double medullary shell, without polar spines or tubes.

The genus Cypassis differs from Cyphonium by duplication of the cortical twin-shell; from the outer surface of the simple twin-shell arise numerous radial spines, which become connected by anastomosing transverse branches, and in this manner form an outer envelope or mantle. Cypassis may also be regarded as a Cromyodruppa, the double cortical shell of which is constricted in the equatorial plane.

Subgenus 1. Didymospyris, Haeckel (1881).

Definition.—Surface of the shell smooth, without thorns or spines.

1. Cypassis palliata, n. sp.

Inner cortical shell thin walled, with regular, circular, hexagonally-framed pores, twice as broad as the bars; seven to eight on the half meridian of each chamber, ten to twelve on its half equator. Outer cortical shell very thin, with smooth surface, and very small, irregular, roundish pores, twice to five times smaller than those of the inner shell. Distance between the two cortical shells equals the diameter of the outer medullary shell, which, like the inner, is spherical. (The network of this species resembles that of Peripanartus amphiconiscus, Pl. 40, fig. 5.)

Dimensions.—Main axis of the external cortical shell 0.18, of the internal 0.12; greatest breadth (in the equator of each chamber) of the former 0.13, of the latter 0.09; pores of the outer 0.002 to 0.005, of the inner shell 0.01, bars 0.002 to 0.005.

Habitat.—South Pacific, Station 288, surface.

2. Cypassis eucolpos, n. sp.

Inner cortical shell thick walled, with regular, circular pores, twice as broad as the bars (without hexagonal frames); nine to ten on the half meridian of each chamber, fifteen to seventeen on its half equator. Outer cortical shell very thin, with smooth surface, and very small, irregular, roundish pores, twice to three times smaller than those of the inner shell. Distance between the two cortical shells about one and a half times the diameter of the inner medullary shell, which, like the outer, is spherical. (The inner cortical shell resembles that of Cannartiscus amphiconiscus, Pl. 39, fig. 19, but without polar tubes.)

Dimensions.—Main axis of the external cortical shell 0.2, of the internal 0.15; greatest breadth of the former 0.16, of the latter 0.12; pores of the outer 0.002, of the inner 0.006, bars 0.003.

Habitat.—South Atlantic, Station 319, surface.

Subgenus 2. Didymocyrtis, Haeckel (1862).

Definition.—Surface of the cortical shell thorny or spiny.

3. Cypassis entomocora, Haeckel.

Astromma entomocora, Ehrenberg, 1847, Mikrogeol., Taf. xxii. fig. 32.

Haliomma didymum, Ehrenberg, 1844, Monatsber. d. k. preuss. Akad. d. Wiss. Berlin, p. 83.

? Haliomma amphisiphon, Ehrenberg, 1844, Monatsber. d. k. Akad. d. Wiss. Berlin, p. 267.

Ommatospyris entomocora, Ehrenberg, 1875, Abhandl. d. k. Akad. d. Wiss. Berlin, pp. 66, 74.

? Ommatocampe trinacria, Stöhr, 1880, Palæontogr., vol. xxvi. p. 90, Taf. ii. fig. 1.

Didymospyris entomocora, Haeckel, 1881, Prodromus.

Didymocyrtis entomocora, Haeckel, 1862, Monogr. d. Radiol., p. 445.

Inner cortical shell thick walled, with regular, circular pores, twice as broad as the bars (without hexagonal frames); eight to nine on the half meridian of each chamber, ten to eleven on its half equator. Outer cortical shell thin walled, with regular, circular pores like those of the inner. Distance between the two cortical shells equals about twice the diameter of one pore (or the short axis of the lenticular double medullary shell). Surface covered with short conical spines (in the figure of Ehrenberg broken off).

Dimensions.—Main axis of the external cortical shell 0.2, of the internal 0.15; greatest breadth of the former 0.13, of the latter 0.1; pores of the outer 0.005 to 0.01, of the inner 0.01, bars 0.004; length of the surface spines 0.005 to 0.01.

Habitat.—Fossil in the Tertiary rocks of Barbados, Bermuda, and Sicily (Caltanisetta); also living in the greatest depth of the Pacific, Stations 268, 225, depth 2900 to 4475.

4. Cypassis puella, n. sp. (Pl. 39, fig. 13).

Didymospyris colpodes, Haeckel, 1881, Prodromus et Atlas (pl. xxxix., fig. 13).

Internal cortical shell thin walled, with irregular, circular pores of very different size, once to four times as broad as the bars; fourteen to fifteen on the half meridian of each chamber, eighteen to twenty on its half equator. Outer cortical shell thin walled, with irregular, circular pores, only one-third to one-half as large as those of the inner. Distance between the two shells equals the largest diameter of the double lenticular medullary shell. Surface of both cortical shells covered with short conical spines (not longer than the largest pores).

Dimensions.—Main axis of the external cortical shell 0.2, of the internal 0.15, of the central capsule 0.1; greatest breadth of the first 0.14, of the second 0.1, of the third 0.07; pores of the outer shell 0.001 to 0.005, of the inner 0.002 to 0.01, bars 0.002 to 0.003; length of the surface spines 0.005 to 0.01.

Habitat.—Pacific, central area; Stations 266 to 274, surface; Atlantic, Canary Islands (Haeckel), Station 354, surface.

5. Cypassis halicora, n. sp.

Internal cortical shell thin walled, with irregular, roundish pores, once to three times as broad as the bars; ten to eleven on half meridian of each chamber, fourteen to sixteen on its half equator. Outer cortical shell thin walled, with very delicate network, spindle-like, with conical prolongations at both poles. Distance between the two shells larger than the greatest diameter of the double lenticular medullary shell. Surface of both cortical shells covered with innumerable small thorns. (Resembles closely Cyphocolpus virginis, Pl. 40, fig. 11, but without the third shell.)

Dimensions.—Main axis of the external cortical shell 0.21, of the internal 0.14, greatest breadth of the former 0.13, of the later 0.09; pores 0.003 to 0.009; bars of the outer shell 0.001, of the inner 0.004.

Habitat.—Indian Ocean, Ceylon (Haeckel), surface.

Genus 158. Cyphocolpus,^[37] n. gen.

Definition.—Cyphinida with triple cortical shell and double medullary shell, without polar spines or tubes.

The genus Cyphocolpus differs from both foregoing genera by the increased number of the cortical twin-shells. Whilst these are simple in Cyphonium, double in Cypassis, they are triple in Cyphocolpus, composed of three concentric envelopes. The three genera named represent a phylogenetic series, which is repeated in the ontogenetic development of Cyphocolpus.

1. Cyphocolpus didymus, n. sp.

Inner cortical shell with circular, subregular pores, twice as broad as the bars; five to six on the half meridian of each chamber, eight to ten on its half equator. Middle cortical shell also with subregular, circular pores of the same size. Outer cortical shell with smooth surface, with more irregular, roundish pores of very different size. The distance between every two shells equals the diameter of the inner medullary shell, which, like the outer, is spheroidal.

Dimensions.—Main axis of the outer cortical shell 0.3, of the middle 0.22, of the inner 0.15; greatest breadth of the inner cortical shell 0.1, its pores 0.01, bars 0.005.

Habitat.—Indian Ocean, Madagascar, Rabbe, surface.

2. Cyphocolpus virginis, n. sp. (Pl. 40, fig. 11).

Zygartus virginis, Haeckel, 1881, Prodromus et Atlas (pl. xl. fig. 11).

Inner cortical shell with irregular, roundish pores, twice to three times as broad as the bars; eleven to twelve on the half meridian of each chamber, sixteen to eighteen on its half equator. Middle cortical shell with very delicate network, its irregular, polygonal pores of the same size as those of the inner, but separated by extremely thin bars. Outer cortical shell with spiny surface, and with more irregular, roundish pores of different size. The distance between each two shells is variable, and attains more than the diameter of the outer medullary shell, which, like the inner, is spheroidal, slightly compressed.

Dimensions.—Main axis of the outer cortical shell 0.26, of the middle 0.22, of the inner 0.14; greatest breadth of the inner cortical shell 0.09, its pores 0.004 to 0.006, bars 0.002.

Habitat.—Pacific, central area, Station 271, surface.

Genus 159. Cyphinus,^[38] Haeckel, 1881, Prodromus, p. 463.

Definition.—Cyphinida with simple cortical shell and simple medullary shell, with two opposite polar spines (or bunches of polar spines) on the poles of the main axis.

The genus Cyphinus differs from Cyphanta by the development of two opposite spines (or bunches of spines) on both poles of the main axis. It simulates therefore the bipolar formation of Stylartus, and differs from this in the possession of a medullary shell.

Subgenus 1. Cyphinoma, Haeckel.

Definition.—On both poles of the main axis only one single large spine.

1. Cyphinus amphacanthus, n. sp.

Cortical shell with smooth surface, and circular, regular pores, twice as broad as the bars; five to six pores on the half meridian of each chamber, ten to twelve on its half equator. On both poles of the main axis, one single, very strong, conical spine, about half as long as this axis, and half as broad at the base as the spherical medullary shell.

Dimensions.—Main axis of the cortical shell (without spines) 0.2, greatest breadth (in the equator of each chamber) 0.1; pores 0.006, bars 0.003; length of the polar spines 0.1, basal thickness of them 0.02.

Habitat.—North Pacific, Station 244, depth 2900 fathoms.

2. Cyphinus dixiphus, n. sp.

Cortical shell with rough surface, and irregular, roundish pores, twice to four times as broad as the bars; eight to nine pores on the half meridian of each chamber, twelve to fourteen on its half equator. On both poles of the main axis, one single, strong, conical spine, with prominent edges at the base, and nearly as broad as the spherical medullary shell, nearly as long as the main axis.

Dimensions.—Main axis (without spines) 0.18, greatest breadth 0.13; pores 0.003 to 0.008, bars 0.002; length of the polar spines 0.16, basal thickness 0.03.

Habitat.—South Pacific, Station 295, depth 1500 fathoms.

Subgenus 2. Cyphinura, Haeckel.

Definition.—On both poles of the main axis a bunch or circle of several spines.

3. Cyphinus amphilophus, n. sp. (Pl. 39, fig. 14).

Cyphinidium amphilophus, Haeckel, 1882, Atlas (pl. xxxix. fig. 14).

Cortical shell thick walled, with rough surface, and subregular, circular pores of different size, twice to five times as broad as the bars; nine to ten pores on the half meridian of each chamber, twelve to fourteen on its half equator. On both poles of the main axis a bunch of six to eight strong conical spines, the largest of which are about as long as the greatest breadth of the shell; their basal part is furrowed, and nearly half as thick as the spherical medullary shell.

Dimensions.—Main axis of the cortical shell (without spines) 0.18 to 0.2, greatest breadth 0.1 to 0.12; pores 0.004 to 0.01, bars 0.002; length of the polar spines 0.04 to 0.12, basal thickness 0.02 to 0.04.

Habitat.—Pacific, central area, Station 271, depth 2425 fathoms.

4. Cyphinus penicillatus, Haeckel.

Ommatospyris penicillata, Ehrenberg, 1872, Monatsber. d. k. preuss. Akad. d. Wiss. Berlin, p. 318; Abhandl. d. k. Akad. d. Wiss. Berlin, Taf. viii. fig. 4.

Cortical shell thin walled, with rough surface, and irregular, polygonal pores, six to eight times as broad as the bars; five to six pores on the half meridian of each chamber, nine to ten on its half equator. Around both poles of the main axis a polar circle of eight to ten divergent radial spines, scarcely thicker than the bars, and about as long as the diameter of the spherical medullary shell. (In the figure of Ehrenberg the network is too thin and the spines too short.)

Dimensions.—Main axis (without spines) 0.1, greatest breadth 0.09; pores 0.008 to 0.014, bars 0.001 to 0.002; length of the spines 0.02 to 0.04.

Habitat.—Pacific, Philippine Sea, 3300 fathoms, Ehrenberg; Station 206, depth 2100 fathoms.

Genus 160. Cyphinidium,^[39] n. gen.

Definition.—Cyphinida with simple cortical shell and double medullary shell, with two opposite polar spines (or bunches of polar spines) on the poles of the main axis.

The genus Cyphinidium differs from Cyphinus only in the duplication of the medullary shell, which is composed of two concentric spheres or somewhat compressed lenticular spheroids. It exhibits therefore the same relation to Cyphinus that Stylatractus in the Druppulida bears to Lithatractus. Possibly the two former genera are derived from the two latter by an annular constriction in the equatorial plane.

Subgenus 1. Cyphinidoma, Haeckel.

Definition.—On both poles of the cortical shell one single polar spine or a bunch of polar spines.

1. Cyphinidium amphistylium, n. sp.

Cortical shell thick walled, with smooth surface, and subregular, circular pores, twice to three times as broad as the bars; eight to ten on the half meridian, sixteen to eighteen on the half equator of each chamber. Both medullary shells spherical. The cortical shell resembles very much that of Cannartiscus amphiconiscus (Pl. 39, fig. 19), but exhibits instead of the hollow polar tubes two strong solid polar spines of conical form, half as long as the main axis, and as broad at the base as the inner medullary shell.

Dimensions.—Main axis of the cortical shell (without polar spines) 0.14, greatest breadth 0.1; pores 0.008, bars 0.004; length of the polar spines 0.08, basal thickness 0.02.

Habitat.—North Pacific, off Japan, Station 241, depth 2300 fathoms.

2. Cyphinidium apicatum, Haeckel.

Ommatospyris apicata, Ehrenberg, 1872, Monatsber. d. k. preuss. Akad. d. Wiss. Berlin, p. 317.

Cortical shell thin walled, with thorny surface, and irregular, polygonal pores, three to five times as broad as the thin bars; eight to nine on the half meridian, thirteen to fifteen on the half equator of each chamber. On both poles a bunch of four to eight strong conical spines, the central of which (in the main axis) is much larger than the others, and twice as long as the diameter of the outer spheroidal medullary shell; size and number of the polar spines is very variable (commonly five to six).

Dimensions.—Main axis (without spines) 0.12, greatest breadth 0.08; pores 0.005 to 0.01, bars 0.002; length of the polar spines 0.02 to 0.06, basal thickness 0.01.

Habitat.—Northern Pacific, Californian Sea, depth 2500 fathoms, Ehrenberg; Station 253, depth 3125 fathoms.

Subgenus 2. Cyphinidura, Haeckel.

Definition.—On both poles of the cortical shell, a circle of divergent polar spines.

3. Cyphinidium coronatum, n. sp.

Cortical shell with thorny surface, and irregular, roundish pores, twice to four times as broad as the bars; seven to eight on the half meridian, eleven to thirteen on the half equator of each chamber. Around both poles of the main axis occurs a circle of ten to twelve strong, radially divergent spines, about as long as the diameter of the outer medullary shell, which, like the inner, is spheroidal. (This species is identical with the younger developmental stage of Panicium coronatum, Pl. 40, fig. 4, before the formation of two distal chambers.)

Dimensions.—Main axis 0.12, greatest breadth 0.1; pores 0.008 to 0.016, bars 0.004; length of the polar spines 0.02, thickness 0.005.

Habitat.—Pacific, central area, Stations 270 to 274, depth 2350 to 2925 fathoms.

Genus 161. Cannartiscus,^[40] n. gen.

Definition.—Cyphinida with simple cortical shell and simple medullary shell, with two hollow fenestrated polar tubes, opposite on both poles of the main axis.

The genus Cannartiscus differs from Cyphanta in the development of two hollow fenestrated tubes, opposite on both poles of the main axis. It simulates therefore the characteristic formation of Cannartus, and differs from this Artiscid in the possession of a medullary shell.

1. Cannartiscus amphiconiscus, n. sp. (Pl. 39, fig. 19).

Cannartidium amphiconiscus, Haeckel, 1882, Atlas (pl. xxxix. fig. 19).

Cortical shell thick walled, smooth, with regular, circular pores, twice as broad as the bars; nine to ten on the half meridian, sixteen to eighteen on the half equator of each chamber. Polar tubes conical, about as long as one single chamber, on the base somewhat broader than the simple spherical medullary shell. Pores of the tubes only one-third as great as those of the chambers.

Dimensions.—Main axis of the cortical shell (without tubes) 0.14, greatest breadth 0.1; pores 0.008, bars 0.004. Length of the polar tubes 0.07, basal breadth 0.04; pores 0.003, bars 0.002.

Habitat.—North Pacific, Station 253, depth 3125 fathoms.

2. Cannartiscus amphicylindrus, n. sp.

Cortical shell thick walled, rough, with subregular, circular pores, twice to four times as broad as the bars; six to seven on the half meridian, ten to twelve on the half equator of each chamber. Polar tubes cylindrical, on the distal end open (broken off?) nearly as long as the main axis, somewhat narrower than the spherical medullary shell. Pores of the tubes much smaller than those of the chambers.

Dimensions.—Main axis (without tubes) 0.17, greatest breadth 0.12; pores 0.006 to 0.012, bars 0.003. Length of the polar tubes 0.15, breadth of them 0.03; pores 0.003, bars 0.002.

Habitat.—Pacific, central area, Station 268, 2900 fathoms; the same form occurs fossil in the rocks of Barbados.

Genus 162. Cannartidium,^[41] n. gen.

Definition.—Cyphinida with simple cortical shell and double medullary shell, with two hollow fenestrated polar tubes, opposite on both poles of the main axis.

The genus Cannartidium differs from Cannartiscus and Cannartus in the duplication of the medullary shell, which is composed of two concentric spheres or compressed lenticular spheroids. The three genera named form therefore one morphological series, with identical cortical shell, and only differing in the absence or presence of a simple or double medullary shell.

Subgenus 1. Cannartidella, Haeckel.

Definition.—Surface of the cortical shell smooth or a little rough, but without spines or fenestrated protuberances.

1. Cannartidium amphiconicum, n. sp.

Cortical shell thick walled, smooth with regular circular pores twice as broad as the bars; eight to nine on the half meridian, fifteen to sixteen on the half equator of each chamber. Polar tubes conical, with smaller pores, tapering towards the closed apex, about as long as one single chamber, at the base one-third as broad as the equatorial constriction. Both concentric medullary shells spherical. (Nearly identical with Cannartiscus amphiconiscus, Pl. 39, fig 19, but differs in the possession of the double medullary shell.)

Dimensions.—Main axis of the cortical shell (without tubes) 0.15, greatest breadth 0.11; pores 0.009, bars 0.004; length of the polar tubes 0.08, basal breadth 0.04.

Habitat.—Pacific, western tropical part, Station 225, depth 4475 fathoms.

2. Cannartidium amphicanna, Haeckel.

"Curious twin Polycystin," Bury, 1862, Polycystins of Barbados, pl. xx. fig. 4.

Cortical shell thick walled, rough, with regular, circular pores, not broader than the bars; six to seven on the half meridian, ten to twelve on the half equator of each chamber. Polar tubes cylindrical, at the distal end open (broken off?), nearly as long as the main axis, about one-third as broad as the equatorial constriction. Both concentric medullary shells spherical.

Dimensions.—Main axis 0.14, greatest breadth 0.11; pores and bars 0.005; length of the polar tubes 0.13, breadth of them 0.03.

Habitat.—Fossil in the Barbados deposits.

3. Cannartidium amphisiphon, Haeckel.

? Haliomma amphisiphon, Ehrenberg, 1844, Monatsber. d. k. preuss. Akad. d. Wiss. Berlin, p. 267.

Cortical shell thick walled, rough, with irregular, roundish pores, twice to five times as broad as the bars; five to six on the half meridian, nine to ten on the half equator of each chamber. Polar tubes conical, with smaller pores, about as long as one single chamber, half as broad at the base as the equatorial constriction. (This deep-sea form is probably identical with that fossil species which Ehrenberg, in 1844, described as Haliomma amphisiphon, and which he afterwards, in 1875, erroneously identified with his Astromma entomocora (= Cypassis entomocora). But the figure given of the latter is quite different from the given diagnosis of the former.)

Dimensions.—Main axis of the cortical shell (without tubes) 0.13, greatest breadth 0.1; pores 0.006 to 0.12, bars 0.003; length of the polar tubes 0.07, basal breadth of them 0.04.

Habitat.—Tropical Atlantic, Antilles, Station 24, depth 390 fathoms; fossil in the Tertiary rocks of Bermuda.

4. Cannartidium bicinctum, n. sp. (Pl. 39, fig. 18).

Cortical shell thick walled, with a thickened ring-shaped protuberance in the greatest breadth of both chambers. Pores subregular, circular, twice to three times as broad as the bars; seven to eight on the half meridian, thirteen to fifteen on the half equator of each chamber. Polar tubes conical, with smaller pores, somewhat shorter than the greatest breath, nearly as thick at the base as the outer spheroidal medullary shell (fig. 18a).

Dimensions.—Main axis (without tubes) 0.12, greatest breadth 0.08; pores 0.003 to 0.006, bars 0.002; length of the polar tubes 0.08, basal thickness 0.03.

Habitat.—South Atlantic, Station 332, depth 2200 fathoms.

Subgenus 2. Cannartidissa, Haeckel.

Definition.—Surface of the cortical shell with conical fenestrated protuberances in the greatest breadth of both chambers.

5. Cannartidium mammiferum, n. sp. (Pl. 39, fig. 16).

Cortical shell-thin walled, having a circle of six to eight conical protuberances in the greatest breadth of both chambers, each of which exhibits a central apical pore, surrounded by a circle of six to eight oblique larger pores. Between the protuberances occur nine to ten pores on the half meridian of each chamber, circular, subregular, twice to three times as broad as the bars. Polar tubes cylindrical, conical at the closed end, with smaller pores, about as long as the greatest breadth of the chambers, as broad as the spherical outer medullary shell.

Dimensions.—Main axis (without tubes) 0.13, greatest breadth (including the protuberances) 0.1; pores 0.005 to 0.008, bars 0.003; length of the polar tubes 0.09, basal thickness 0.02.

Habitat.—Pacific, central area, Station 268, depth 2900 fathoms.

6. Cannartidium mastophorum, n. sp. (Pl. 39, fig. 17).

Cortical shell thin walled, of the same form and structure as in the foregoing species, differs from this mainly in the form of the polar tubes, which are not cylindrical but conical, tapering gradually from the base towards the closed apex. Besides this, the conical protuberances (six in the greatest periphery of each chamber) are more regular and acute, with smaller and more numerous pores. Both medullary shells are here also spherical.

Dimensions.—Main axis (without tubes) 0.14, greatest breadth (including the protuberances) 0.13; pores 0.006 to 0.009, bars 0.004; length of the polar tubes 0.07, basal thickness 0.03.

Habitat.—Pacific, central area, Station 266, depth 2750 fathoms.

Family XVI. Panartida, Haeckel (Pl. 40, figs. 1-9).

Definition.—Prunoidea with a four-jointed cortical shell, the external shell being divided by three parallel transverse constrictions into four chambers, in the centre enclosing two internal concentric shells (medullary shells). Central capsule cylindrical, commonly four-jointed (with three transverse annular constrictions).

The family Panartida (Pl. 40, figs. 1-9) is characterised by its four-jointed cortical shell, constantly composed of four chambers, lying one behind another in the elongated main axis. They are separated by three ring-like constrictions lying in three parallel transverse planes; the middle of these is the equatorial plane. In the centre of this latter lies constantly a double medullary shell.

The Panartida must be derived from the Cyphinida by further increase in the longitudinal or main axis, and by repetition of the equatorial constriction in two transverse planes parallel to it and at an equal distance from it.

The Medullary Shell is always double in this family, composed of two small concentric shells lying in the middle of the central capsule. They are either spherical or lenticular, compressed towards both poles of the main axis; sometimes the inner is spherical, the outer lenticular. From the equatorial circumference of the latter starts a number of radial beams, which perforate the central capsule, and are inserted into the equatorial constriction of the cortical shell. Commonly all radial beams lie in the equatorial plane, sometimes also a part of them on both sides of it.

The Cortical Shell is constantly composed of four completely latticed chambers, which are only separated by the three annular constrictions. In many species all four chambers have the same form and size (Pl. 40, fig. 3), but in the greater number of species both proximal (or central) chambers are different in size, shape, or structure from both distal (or polar) chambers. The cortical shell is either simple or double, composed of two concentric four-jointed shells; rarely it is triple or multiple, composed of three or more shells fitting one inside the other. Very often the outer cortical shell is incomplete, and only developed around the two proximal chambers of the complete inner cortical shell, both distal chambers of the latter remaining simple.

On both poles of the main axis often are developed solid spines (Panicium, Pl. 40, fig. 4) or hollow fenestrated tubes (Panarium, Pl. 40, fig. 9), as in the foregoing families. Besides this, the surface of the cortical shell may be armed with spines.

The Central Capsule of the Panartida is always cylindrical, on both poles hemispherical; commonly it is more or less distinctly four-jointed, with three ring-like constrictions corresponding to those of the enclosing cortical shell. From the inner surface of the latter it is separated by a thinner or thicker jelly-mantle.

Synopsis of the Genera of Panartida.

On both poles of the main axis neither peculiar polar spines nor fenestrated tubes.	$\scriptstyle {\left\{{\begin{matrix}\ \\\\\ \ \end{matrix}}\right.}$	Cortical shell simple,	163. Panartus.
		Cortical shell double or triple,	164. Peripanartus.
On both poles of the main axis a large apical spine or a group of polar spines.	$\scriptstyle {\left\{{\begin{matrix}\ \\\\\ \ \end{matrix}}\right.}$	Cortical shell simple,	165. Panicium.
		Cortical shell double or triple,	166. Peripanicium.
On both poles of the main axis a conical or cylindrical fenestrated tube.	$\scriptstyle {\left\{{\begin{matrix}\ \\\\\ \ \end{matrix}}\right.}$	Cortical shell simple,	167. Panarium.
		Cortical shell double or triple,	168. Peripanarium.

Genus 163. Panartus,^[42] n. gen.

Definition.—Panartida with simple cortical shell and double medullary shell, without polar spines or tubes on both poles of the main axis.

The genus Panartus represents the common ancestral form of all Panartida, as all other genera of this subfamily must be derived from it and are only further developmental stages, from an ontogenetic as well as from a phylogenetic point of view. The cortical shell of Panartus is constantly composed of four fenestrated chambers jointed to one another in the main axis; both proximal chambers are separated from one another by the equatorial ring-like constriction, in the centre of which lies the double medullary shell; both distal chambers are separated from the former by two other annular constrictions (in planes parallel to the equatorial plane). All four chambers may exhibit the same (kidney-shaped) form and structure (in the subgenera Panartella and Panartoma); or the proximal chamber may differ more or less in shape and size from the distal (in the subgenera Panartissa and Panartura). The outer surface of the cortical shell is sometimes smooth (as in Panartella and Panartissa), at other times spiny or thorny (as in Panartoma and Panartura). The double medullary shell is sometimes spherical, or commonly compressed at both poles and spheroidal or lenticular.

Subgenus 1. Panartella, Haeckel.

Definition.—Surface of the cortical shell smooth, without spines or thorns. All its four chambers exhibit nearly the same form and structure.

1. Panartus tetraplus, n. sp.

All four chambers of the cortical shell of the same form, size, and structure, kidney-shaped, twice as broad as long. Pores rather regular, hexagonal, all nearly of the same size and form, four times as broad as the thin bars; five to six pores on the half meridian, nine to ten on the half equator of each chamber. Surface of the cortical shell smooth, its main axis three times as long as its equatorial axis (in the median constriction). Both concentric medullary shells spherical; the equatorial axis of the outer half as long as that of the cortical shell. (All four chambers of this species have the same appearance as the two proximal chambers of Panartus diploconus, Pl. 40, fig. 1.)

Dimensions.—Main axis of the cortical shell 0.21, equatorial axis 0.07; breadth of every chamber 0.09; meshes 0.013, bars 0.03.

Habitat.—Central area of the Pacific, Stations 270 to 274, depth 2350 to 2925 fathoms.

2. Panartus tetracolus, n. sp.

All four chambers of the cortical shell of the same form, size, and structure, kidney-shaped, twice as broad as long. Pores regular, circular, with hexagonal frame, twice as broad as the bars; six to seven pores on the half meridian, ten to twelve on the half equator of each chamber. Surface of the cortical shell smooth; its main axis three times as long as the equatorial axis. Both concentric medullary shells spheroidal, somewhat compressed at both poles; the equatorial axis of the outer almost equals half that of the cortical shell. (All four chambers of this species exhibit the structure of the two proximal chambers of Peripanartus amphiconus, Pl. 40, fig. 5.)

Dimensions.—Main axis of the cortical shell 0.24, equatorial axis 0.08; breadth of every chamber 0.01; meshes 0.01, bars 0.005.

Habitat.—Equatorial Atlantic, Station 348, depth 2450 fathoms.

3. Panartus tetrameres, n. sp.

All four chambers of the cortical shell of the same form, size, and structure, kidney-shaped, twice as broad as long. Pores rather regular, circular, without hexagonal frame, about as broad as the bars; five to six pores on the half meridian, ten to twelve on the half equator of each chamber. Surface of the cortical shell smooth, its main axis three times as long as the equatorial axis. Both concentric medullary shells spheroidal, compressed; the outer half as broad as the constriction. (This species is very much like Ommatocampe increscens, Stöhr, 1880, loc. cit., Taf. ii. fig. 2, and may be considered as the ancestral form of it.)

Dimensions.—Main axis of the cortical shell 0.2, equatorial axis 0.065; breadth of every chamber 0.08; meshes and bars 0.005.

Habitat.—Fossil in the Tertiary rocks of Sicily, Caltanisetta, Haeckel.

4. Panartus tetraphalangus, n. sp.

All four chambers of the cortical shell of the same form, size, and structure, kidney-shaped, twice as broad as long. Pores irregular, polygonal (mostly pentagonal or hexagonal), four to eight times as broad as the thin bars; four to seven on the half meridian, eight to fifteen on the half equator of each chamber. Surface of the cortical shell smooth, its main axis three times as long as its equatorial axis. Both concentric medullary shells compressed, the outer, half as broad as the constriction.

Dimensions.—Main axis of the cortical shell 0.26, equatorial axis 0.09; breadth of every chamber 0.12; meshes 0.003 to 0.02, bars 0.001 to 0.003.

Habitat.—Fossil in the rocks of Barbados, Haeckel.

5. Panartus tetrathalamus, n. sp. (Pl. 40, fig 3).

All four chambers of the cortical shell of the same form, size, and structure, kidney-shaped, twice as broad as long. Pores irregular, roundish, twice to three times as broad as the bars; a circle of larger pores at the base of both distal chambers; five to six pores on the half meridian, ten to twelve on the half equator of each chamber. Surface of the cortical shell smooth; its main axis two and a half times as long as the equatorial axis. Both medullary shells spheroidal, compressed, the outer one-third as broad as the constriction. (In the specimen figured spines begin to arise from both distal chambers; this forms a transition to Panartus quadrijugus.)

Dimensions.—Main axis of the cortical shell 0.18, equatorial axis 0.07; breadth of every chamber 0.09; meshes 0.003 to 0.01, bars 0.002 to 0.004.

Habitat.—Cosmopolitan; Mediterranean, Atlantic, Pacific, in various depths.

Subgenus 2. Panartissa.

Definition.—Surface of the cortical shell smooth, without spines or thorns. Both its proximal chambers differ in form and structure from the two distal chambers.

6. Panartus diploconus, n. sp. (Pl. 40, fig. 1).

Both proximal chambers nearly ellipsoidal, one and a half times as broad as long, with regular hexagonal pores, four times as broad as the bars; five to six pores on the half meridian, nine to ten on the half equator of each chamber. Both distal chambers conical, with a circle of ten to twelve large square pores at the base; the other pores very small and numerous, roundish, sixteen to twenty in the height of each cone, and the same number on the half periphery of its base. Both concentric medullary shells compressed, the outer, half as broad as the constriction of the cortical shell, the surface of which is quite smooth.

Dimensions.—Total length of the shell (or main axis) 0.34; greatest breadth of each chamber 0.09; pores of the proximal chambers 0.013, bars 0.003; pores and bars of the distal chambers 0.003; large basal square pores 0.02.

Habitat.—Pacific, central area, Station 272, depth 2600 fathoms.

7. Panartus amphiconus, n. sp.

Both proximal chambers nearly kidney-shaped, one and a half times as broad as long, with regular, circular pores, with hexagonal frames, twice as broad as the bars; six to seven pores on the half meridian, ten to twelve on the half equator of each chamber. Both distal chambers conical, with a circle of ten to twelve very large pores at the base; the other pores very small, roundish, ten to fifteen in the height of each cone, twenty to thirty on the half basal periphery. Both concentric medullary shells compressed, the outer one-third as broad as the constriction of the cortical shell, whose surface is smooth. (This species resembles Peripanartus amphiconus, Pl. 40, fig. 5, but is without the surface spines and the outer envelope.)

Dimensions.—Total length of the shell 0.28; greatest breadth of the proximal chambers 0.1, of the distal chambers 0.14; pores of the former 0.008, of the latter 0.004; bars of both 0.003 to 0.005.

Habitat.—North Pacific, Station 244, depth 2900 fathoms.

8. Panartus fusiformis, n. sp.

Both proximal chambers nearly ellipsoidal, one and a half times as long as broad, with irregular, roundish pores, twice to three times as broad as the bars; eight to ten pores on the half meridian, twelve to fifteen on the half equator of each chamber. Both distal chambers hemiellipsoidal or egg-shaped, somewhat higher and narrower than the proximal chambers, with a circle of larger square pores at their base; the other pores roundish and very irregular. Both medullary shells spheroidal, one-third as broad as the constriction of the cortical shell, whose surface is quite smooth. (This species is similar to Peripanartus atractus, Pl. 40, fig. 7, but is without the superficial spines and the equatorial girdle-like envelope of the latter.)

Dimensions.—Total length of the shell 0.25 to 0.3; greatest breadth (in the equator of the proximal chambers) 0.08 to 0.1; pores of the proximal chambers 0.008 to 0.012, pores of the distal chambers half their size, bars 0.002 to 0.006.

Habitat.—North Pacific, Station 237, surface.

9. Panartus profundissimus, Haeckel.

Ommatocampe profundissima, Ehrenberg, 1872, Abhandl. d. k. Akad. d. Wiss. Berlin, p. 297, Taf. viii. fig. 6.

Both proximal chambers nearly ellipsoidal, with irregular, polygonal pores, six to eight times as broad as the bars; four to five pores on the half meridian, eight to nine on the half equator of each chamber. Both distal chambers hemispherical, with a very delicate irregular network. Medullary shells spherical; surface of the shell smooth.

Dimensions.—Total length of the shell 0.15; greatest breadth in the equator of the proximal chambers 0.08; pores of the proximal chambers 0.015, bars 0.002.

Habitat.—Philippine Sea, depth 3300 fathoms, Ehrenberg; Station 213, depth 2050 fathoms.

Subgenus 3. Panartoma, Haeckel.

Definition.—Surface of the cortical shell thorny, covered with scattered spines. All its four chambers exhibit the same form and structure.

10. Panartus quadriceps, n. sp.

All four chambers of the cortical shell of the same form, size, and structure, kidney-shaped, twice as broad as long. Pores rather regular, circular, with hexagonal frames, twice to three times as broad as the bars; six to seven pores on the half meridian, ten to twelve on the half equator of each chamber. Surface spiny; from the corners of the hexagonal frames (between every three pores) arise short radial spines. Both medullary shells spherical, the outer one-third as broad as the constriction of the cortical shell. (All the four chambers of this species have the same form as the two proximal chambers of Peripanartus amphiconus, Pl. 40, fig. 5.)

Dimensions.—Main axis of the cortical shell 0.24, equatorial axis 0.08; meshes 0.01, bars 0.003 to 0.005; length of the spines 0.01 to 0.02.

Habitat.—Pacific, central area, Station 274, depth 2750 fathoms.

11. Panartus quadrijugus, n. sp.

All four chambers of the cortical shell of the same form and size, kidney-shaped, twice as broad as long. Pores irregular, roundish, twice to three times as broad as the bars; a circle of larger pores at the base of both distal chambers; six to eight pores on the half meridian, twelve to fourteen on the half equator of each chamber. Surface spiny, everywhere covered with small irregular thorns. (This species differs from the smooth Panartus tetrathalamus, Pl. 40, fig. 3, almost entirely by the thorny surface.)

Dimensions.—Main axis 0.2, equatorial axis 0.08; breadth of every chamber 0.1; meshes 0.005 to 0.01, bars 0.003, spines 0.01 to 0.02.

Habitat.—Cosmopolitan; on the surface of the Atlantic, Indian, and Pacific Oceans.

12. Panartus quadrigeminus, n. sp.

All four chambers of the cortical shell nearly of the same size and form, kidney-shaped, twice as broad as long. Pores irregular, polygonal (mostly pentagonal or hexagonal), six to eight times as broad as the thin bars; five to seven on the half meridian, twelve to sixteen on the half equator of each chamber. Surface of the cortical shell spiny, covered with numerous irregularly scattered, often oblique, bristle-like thorns.

Dimensions.—Main axis 0.27, equatorial axis 0.1; breadth of each chamber 0.13; meshes 0.01 to 0.02, bars 0.001 to 0.005.

Habitat.—Cosmopolitan; surface of the Atlantic and Pacific, many Stations.

Subgenus 4. Panartura, Haeckel.

Definition.—Surface of the cortical shell thorny, covered with scattered spines. Both its proximal chambers differ in form or structure from the two distal chambers.

13. Panartus spinosus, n. sp.

Both proximal chambers nearly ellipsoidal, with regular, circular pores enclosed by hexagonal frames. Both distal chambers conical, with a circle of ten to twelve large square pores at the base; the other pores small, roundish. The cortical shell of this species is quite the same as that of Panartus amphiconus (Pl. 40, fig. 5), but differs in the absence of the external envelope (or the second cortical shell), and is covered with short, conical spines on the whole surface.

Dimensions.—Total length of the cortical shell 0.25, greatest breadth (on the base of the distal chambers) 0.12; meshes of the proximal chambers 0.008, of the distal chambers 0.004; bars 0.002 to 0.04, spines 0.01 to 0.02.

Habitat.—North Pacific, Station 240, surface.

14. Panartus setosus, Haeckel.

Ommatocampe setosa, Ehrenberg, 1872, Abhandl. d. k. Akad. d. Wiss. Berlin, p. 297, Taf. viii. fig. 7.

Both proximal chambers kidney-shaped, broader than the two hemispherical distal chambers. Meshes of the cortical shell irregular, polygonal, or subregular hexagonal; at the base of each distal chamber a circle of large square meshes. The breadth of the pores is eight to twelve times that of the bars between them. The whole surface is covered with small bristle-like spines.

Dimensions.—Total length of the cortical shell 0.14, greatest breadth (in the equator of each proximal chamber) 0.07; meshes 0.008 to 0.015, bars 0.002, spines 0.01.

Habitat.—Pacific (Philippine and Californian Sea) 3300 and 2300 fathoms, Ehrenberg; Station 200, depth 250 fathoms; Station 253, depth 3125 fathoms.

15. Panartus pluteus, n. sp. (Pl. 40, fig. 2).

Both proximal chambers kidney-shaped, with irregular, roundish pores, twice to four times as broad as the bars; their surface everywhere covered with short conical thorns. From both polar circles arise ten to twelve radial rods, which bear a fenestrated cap, and form thus either the beginning of a second, external, cortical shell, or (if remaining thus) two imperfect distal chambers. The spherical segment, which forms their surface, is concentric with the proximal chambers, is perforated by the same irregular, roundish pores, and covered with numerous bristle-like spines.

Dimensions.—Main axis of the cortical shell 0.17, equatorial axis (in the constriction) 0.06; distance between the proximal and distal chambers 0.03; pores 0.003 to 0.01, bars 0.003 to 0.005.

Habitat.—Pacific, central area, Station 272, depth 2600 fathoms.

Genus 164. Peripanartus,^[43] n. gen.

Definition.—Panartida with double cortical shell and double medullary shell, without polar spines or tubes on both poles of the main axis.

The genus Peripanartus differs from Panartus only in the development of an outer reticulated envelop, which mantle-like surrounds the shell and represents a second or external cortical shell. This mantle or veil envelops either the whole internal cortical shell or only both proximal chambers. Peripanartus exhibits the same relation to Panartus as in the foregoing ancestral family Cypassis bears to Cyphonium.

Subgenus 1. Peripanartula, Haeckel.

Definition.—-Surface of the outer cortical shell smooth, without spines or thorns.

1. Peripanartus palliatus, n. sp.

Internal cortical shell with four kidney-shaped chambers of equal size and similar form, identical with the cortical shell of Panartus tetrathalamus and Panartus quadrijugus (Pl. 40, fig. 3), with irregular, roundish pores, twice to three times as broad as the bars. It differs from these two species only by the external cortical shell enveloping the whole internal one, in the same manner as in Peripanartus cylindrus (Pl. 40, fig. 6). The two shells are connected by numerous radial rods. The surface of the outer cortical shell is quite smooth, its irregular, roundish pores about half as large as those of the inner cortical shell.

Dimensions.—Main axis of the external cortical shell 0.27, of the internal 0.2; greatest breadth of the former (in the equator of each chamber) 0.13, of the latter 0.09; pores of the external cortical shell 0.002 to 0.004, of the internal 0.004 to 0.008; bars of the former 0.002, of the latter 0.003.

Habitat.—Pacific, central area, Stations 271, 272, depth 2425 to 2600 fathoms.

2. Peripanartus lævigatus, n. sp.

Internal cortical shell with four unequal chambers, both proximal kidney-shaped (with subregular polygonal pores, twice to three times as broad as the bars), both distal nearly hemispherical, with subregular, roundish pores of half that size. External cortical shell envelops only the proximal chambers, and appears as the direct continuation of the internal shell of the distal chambers, with the same small roundish pores. The outer surface is quite smooth. This species has nearly the same structure as Peripanicium amphicorona (Pl. 40, fig. 8), but differs from it by the absence of the polar spine-circles, and by the perfect smoothness of the surface.

Dimensions.—Main axis of the shell 0.25, greatest breadth (in the equator of the proximal chambers) 0.15; equatorial stricture of the external shell 0.10, of the internal 0.07; pores of the internal shell of the proximal chambers 0.013, of the external 0.006; bars 0.003.

Habitat.—Pacific, central area, Station 274, depth 2750 fathoms.

3. Peripanartus amphiconus, n. sp. (Pl. 40, fig. 5).

Inner cortical shell with four very unequal chambers; both proximal chambers kidney-shaped (with regular, circular, hexagonally framed pores, twice as broad as the bars); both distal chambers conical, with a circle of large square pores at the base, the other pores very small, roundish. Outer cortical shell very thin, quite smooth, with irregular, roundish pores, envelops in younger specimens only the distal chambers. But the radial spines on the surface of the internal cortical shell of the proximal chambers indicate that these will also be afterwards enclosed by the growing of the external shell. This species exhibits the progressive (ontogenetic as well as phylogenetic) development of Panartus amphiconus.

Dimensions.—Main axis of the outer cortical shell 0.3, its greatest breadth (at the prominent distal ends of the radial rods between the large square pores) 0.15; pores 0.003 to 0.001, bars 0.005; main axis of the inner cortical shell 0.26, its greatest breadth 0.13; pores of its distal chambers 0.003, of its proximal chambers 0.01; large square pores 0.03; bars 0.004.

Habitat.—Pacific, central area, Station 270, depth 2925 fathoms.

Subgenus 2. Peripanartium, Haeckel.

Definition.—Surface of the outer cortical shell covered with spines or thorns.

4. Peripanartus atractus, n. sp. (Pl. 40, fig. 7).

Inner cortical shell with four very unequal chambers; both proximal chambers spheroidal (with subregular, roundish pores, twice to three times as broad as the bars), both distal chambers nearly conical, with a circle of eight to ten very large square pores at the base; the other pores very small, roundish. Outer cortical shell envelops only the proximal chambers and the basal half of the distal chambers, appearing as the direct continuation of the microporous covering of their apical half. The whole external cortical shell is inflated in the equatorial zone, and hence assumes an irregular, spindle-like appearance. Its whole surface is rough with innumerable very short thorns.

Dimensions.—Main axis 0.28, equatorial axis 0.17; pores of the external cortical shell 0.002 to 0.004, bars 0.002; main axis of the proximal chambers of the internal cortical shell 0.07, equatorial axis 0.09; pores 0.007, bars 0.004.

Habitat.—North Pacific, Station 244, depth 2900 fathoms.

5. Peripanartus cylindrus, n. sp. (Pl. 40, fig. 6).

Internal cortical shell with four unequal chambers; both proximal chambers kidney-shaped (with regular, circular, hexagonally framed pores of the same breadth as the bars), both distal chambers nearly hemispherical, with a circle of eight to ten very large square pores at their base; the other pores very small, roundish. External cortical shell envelops the whole internal like a perfect hollow cylinder, which is closed at both poles by a hemispherical cap. The whole surface of this cylindrical mantle is perforated by innumerable very small roundish pores, and covered with small bristle-like spines.

Dimensions.—Main axis of the cylinder 0.3, equatorial axis 0.12; pores and bars 0.006; spines of its surface 0.012 to 0.15; main axis of the internal cortical shell 0.2; equatorial axis (in the constriction) 0.06; pores and bars of its proximal chambers 0.007, of its distal chambers 0.003; large square pores at their base 0.02.

Habitat.—Pacific, central area, Stations 270 to 274, depth 2350 to 2925 fathoms.

Genus 165. Panicium,^[44] n. gen.

Definition.—Panartida with simple cortical shell and double medullary shell, with two opposite apical spines on both poles of the main axis, or with a group of polar spines.

The genus Panicium comprises those forms of Panartus which develop a peculiar armature on both poles of the cortical shell. This may be only a single strong spine on each pole, lying in the main axis (subgenus Panicidium); or a bunch or a circle of polar spines diverging radially (subgenus Panartidium); in the latter case the polar spines can either form a bunch on the pole itself, or a crown of thorns around it.

Subgenus 1. Panicidium, Haeckel.

Definition.—On both poles of the main axis only a single large spine.

1. Panicium amphacanthum, n. sp.

All four chambers of the cortical shell nearly of the same size and form, kidney-shaped, with subregular, circular pores, twice as broad as the bars; five to six pores on the half meridian, ten to eleven on the half equator of each chamber. Surface covered with small spines. On both poles of the main axis is a very strong, conical, apical spine, half as long as the main axis, on the base one-fourth as broad as the equatorial axis.

Dimensions.—Main axis (without polar spines) 0.22, equatorial axis 0.06; pores 0.01, bars 0.005; length of the polar spines 0.12, basal thickness 0.015.

Habitat.—Antarctic, Station 152, depth 1260 fathoms.

2. Panicium amphistylus, n. sp.

Both proximal chambers kidney-shaped, both distal chambers nearly hemispherical, somewhat smaller. Pores irregular, roundish, twice to three times as broad as the bars; four to six on the half meridian, eight to ten on the half equator of each chamber; a circle of larger square pores on the base of each distal chamber. Surface thorny. On both poles of the main axis one strong, pyramidal, apical spine, one-third as long as the main axis, on the base one-fourth as broad as the equatorial constriction. (Similar to Panarium tubularium, Pl. 40, fig. 9, but without tubes.)

Dimensions.—Main axis (without polar spines) 0.2, equatorial axis 0.05; pores 0.005 to 0.01, bars 0.003; length of the polar spines 0.07, basal thickness 0.012.

Habitat.—Antarctic, Station 156, depth 1975 fathoms.

Subgenus 2. Panartidium, Haeckel.

Definition.—On both poles of the main axis a bunch or a circle of aggregated spines.

3. Panicium scoparium, n. sp.

Both proximal chambers kidney-shaped, both distal chambers nearly hemispherical, somewhat smaller. Pores irregular, polygonal, twice to five times as broad as the bars; six to eight on the half meridian, twelve to fourteen on the half equator of each chamber. Surface spiny, covered with thin, bristle-like spines. On both poles of the main axis a bunch of six to eight aggregated larger conical spines, about as high as a single chamber.

Dimensions.—Main axis (without polar spines) 0.2, equatorial axis 0.06; pores 0.005 to 0.015, bars 0.003; length of the polar spines 0.05, basal thickness 0.005.

Habitat.—Pacific, central area, Stations 270 to 274, depth 2350 to 2925 fathoms.

4. Panicium coronatum, n. sp. (Pl. 40, fig. 4).

Both proximal chambers kidney-shaped, covered with short stout spines. Pores irregular, roundish, twice to four times as broad as the bars; seven to eight on the half meridian, eleven to thirteen on the half equator of each chamber. Both distal chambers cap-like, separated from the former by a circle of ten to twelve very large square pores; the other pores very small, roundish. The circumpolar area is smooth, surrounded by a circle of ten to twelve very stout, conical, radial spines, which arise from the distal ends of the bars separating the large square meshes.

Dimensions.—Main axis (without spines) 0.22, equatorial axis 0.08; greatest breadth in the equator of the chambers 0.1; pores of the proximal chambers 0.007 to 0.015, bars 0.004; square pores of the distal chambers 0.02 to 0.03, small pores 0.005, bars 0.004; length of the radial spines of the polar circles 0.07, basal thickness 0.007.

Habitat.—Pacific, central area, Station 271, depth 2425 fathoms.

Genus 166. Peripanicium,^[45] n. gen.

Definition.—Panartida with double cortical shell and double medullary shell, on both poles of the main axis with two opposite apical spines, or with a bunch or circle of polar spines.

The genus Peripanicium differs from Panicium only in the development of an outer reticulated envelope, which mantle-like surrounds the shell, and represents a second or external cortical shell. As in Panicium, its ancestral form, so also in Peripanicium, there can be distinguished two subgenera:—Peripanicea, where only a single large spine arises from each pole (lying in the main axis), and Peripanicula, where a variable number of spines is to be found, either diverging bunch-like from the pole itself, or surrounding it as a crown-like polar circle.

Subgenus 1. Peripanicea, Haeckel.

Definition.—On both poles of the main axis only a single large spine.

1. Peripanicium amphixiphus, n. sp.

Internal cortical shell with four unequal chambers, with thorny surface. Both proximal chambers kidney-shaped (with subregular hexagonal pores, three times as broad as the bars). Both distal chambers nearly hemispherical (with a circle of ten to twelve very large square pores at their base, the other pores very small). From both poles arises a single, strong, conical spine, half as long as the main axis. The internal cortical shell is very much like that of Panarium tubularium (Pl. 40, fig. 9), but differs by the solid polar spines (instead of the hollow tubules) and by the formation of an external, cylindrical, very thin, cortical shell, which envelops the whole internal, and is connected with it by numerous beams. The surface of the external shell is quite smooth, and perforated by innumerable very small roundish pores.

Dimensions.—Main axis of the external cortical shell 0.25, of the internal 0.19; transverse axis of the former 0.13, of the latter 0.08; pores of the proximal chambers of the internal shell 0.01, bars 0.003; pores of external cortical shell 0.002, bars 0.001; length of both polar spines 0.12, basal thickness of them 0.02.

Habitat.—South Atlantic, near Tristan da Cunha, Station 333, depth 2025 fathoms.

Subgenus 2. Peripanicula, Haeckel.

Definition.—On both poles of the main axis a bunch or a circle of aggregated polar spines.

2. Peripanicium amphicorona, n. sp. (Pl. 40, fig. 8).

Peripanartus amphicorona, Haeckel, 1881, Prodromus et Atlas (pl. xl. fig. 8).

Internal cortical shell with four very unequal chambers. Both proximal chambers kidney-shaped, with subregular, polygonal pores, three times as broad as the bars. Both distal chambers double cone-shaped; the proximal cone of these formed by a circle of ten to twelve radial beams, which separate the same number of large square meshes; the distal cone with five to six circles of very small roundish, irregular pores. The continuation of the thin porous lamella of this distal cone forms the external cortical shell, whose surface is a little rough with innumerable very small thorns. On both poles is a large circular opening (nearly as broad as the equatorial constriction of the inner shell), surrounded by a delicate crown of thorns. The spines of this crown equal the diameter of the polar opening; they are very thin and bristle-like, connected by a few bridges and diverge outwards.

Dimensions.—Main axis (without the crowns of polar thorns) 0.26, greatest breadth (in the equator of the proximal chambers) 0.15; equatorial constriction of the external shell 0.12, of the internal 0.07; pores of the proximal chambers of the internal cortical shell 0.01, of the external 0.005, bars 0.003; diameter of the circular polar opening 0.05; length of the polar spines 0.05.

Habitat.—Pacific, central area, Station 271, depth 2425 fathoms.

3. Peripanicium coronarium, n. sp.

Internal cortical shell with four unequal chambers. Both proximal chambers kidney-shaped, with irregular, roundish pores, twice to four times as broad as the bars. Both distal chambers cap-like, with a basal circle of ten to twelve large square meshes, the other pores very small. External cortical shell very thin, with smooth surface, and very small, irregular, roundish pores; it envelops the whole internal shell at a constant distance, which equals the breadth of the square meshes. From the distal ends of the radial beams between the square meshes arise on every polar circle ten to twelve strong spines, as direct prolongations of those beams. These form two regular, polar crowns of thorns. The inner part of the thorns (between both shells) has only one-third to one-fourth the length of the outer free part. (This species represents a further development of Panicium coronatum, Pl. 40, fig. 4, by secondary formation of an external mantle, like that of Peripanartus atractus, Pl. 40, fig. 7.)

Dimensions.—Main axis 0.27, greatest breadth 0.15; pores of the internal proximal chambers 0.008 to 0.016, bars 0.004; square meshes of the distal chambers 0.03; pores of the outer cortical shell 0.003; length of the spines of the polar circles 0.1 to 0.15.

Habitat.—Pacific, central area, Station 274, depth 2750 fathoms.

Genus 167. Panarium,^[46] Haeckel, 1881, Prodromus, p. 463.

Definition.—Panartida with simple cortical shell and double medullary shell, with two hollow fenestrated tubes, opposite on the poles of the main axis.

The genus Panarium differs from Panartus by two hollow latticed tubes, which start from both poles of the main axis and lie in it. It repeats therefore in this family the same peculiar and remarkable formation, which we find in Pipettella among the Ellipsida, in Pipetta among the Druppulida, in Cannartidium among the Cyphinida, in Cannartus among the Artiscida, &c.

Subgenus 1. Panarelium, Haeckel.

Definition.—Surface of the shell smooth, without spines or thorns.

1. Panarium facettarium, n. sp.

Surface of the cortical shell smooth. All the four chambers nearly of the same size and form, kidney-shaped, about twice as broad as long. Pores of these subregular, circular, with hexagonal frames, about as broad as the bars; nine to ten on the half meridian, twelve to fourteen on the half equator of each chamber. Polar tubuli nearly cylindrical, longer than half the main axis of the cortical shell, about one-fourth as broad as the equatorial constriction. Pores of the tubuli of the same shape as those of the chambers, but only half as large. (This species is like Pipetta tuba, Pl. 39, fig. 7, but distinguished by three parallel transverse constrictions.)

Dimensions.—Total length of the shell (without tubuli) 0.26; breadth of each chamber 0.12; pores 0.01, bars 0.01; length of the tubuli 0.15, breadth of them 0.03.

Habitat.—Pacific central area, Station 268, depth 2900 fathoms.

2. Panarium pipettarium, n. sp.

Surface of the cortical shell smooth. Both proximal chambers nearly kidney-shaped; both distal chambers somewhat smaller, hemispherical. Pores of all four chambers subregular, circular, without hexagonal frames, twice as broad as the bars; six to seven pores on the half meridian, ten to eleven on the half equator of each chamber. Polar tubuli slender, conical, nearly half as long as the main axis of the shell, one-third as broad at the base as the equatorial constriction. Pores of the tubuli of the same shape as those of the chambers, but only half as large. (This species resembles somewhat Cannartiscus amphiconiscus, Pl. 39, fig. 19, but with double the number of chambers.)

Dimensions.—Total length of the shell (without tubuli) 0.25, greatest breadth 0.1; pores 0.008, bars 0.004; length of the polar tubuli 0.11, basal breadth 0.03.

Habitat.—Pacific, western tropical part, Station 225, depth 4475 fathoms.

Subgenus 2. Panaromium, Haeckel.

Definition.—Surface of the shell spiny, covered with short thorns.

3. Panarium annularium, n. sp.

Surface of the cortical shell thorny, everywhere covered with small bristle-like spines. All four chambers nearly of the same size and form, kidney-shaped. Their pores subregular, circular, three to four times as broad as the bars; seven to eight on the half meridian, ten to eleven on the half equator of each chamber. Polar tubuli conical, nearly half as long as the main axis, half as broad at the base as the equatorial constriction. Pores of the tubuli like those of the chambers, but only half as broad.

Dimensions.—Total length of the shell (without tubuli) 0.16; breadth of each chamber 0.07; pores 0.006 to 0.008, bars 0.002; length of the polar tubuli 0.07, basal breadth 0.03.

Habitat.—Northern Pacific, Station 253, depth 3125 fathoms.

4. Panarium artophorum, n. sp.

Surface of the shell thorny, with scattered small spines. Both proximal chambers nearly kidney-shaped; both distal hemispherical, somewhat smaller. Pores of all chambers irregular, roundish, little broader than the bars; four to five on the half meridian, six to eight on the half equator of each chamber. Polar tubuli cylindrical, longer than the half main axis, only one-fourth as broad the equatorial constriction. Pores of the tubuli only one-third to one-fourth as broad as those of the chambers.

Dimensions.—Total length of the shell (without tubuli) 0.22, greatest breadth (in the equator of the proximal chambers) 0.09; pores and bars 0.008 to 0.012; length of the polar tubuli 0.14, breadth of them 0.02.

Habitat.—Southern Pacific, Station 289, depth 2550 fathoms.

5. Panarium tubularium, n. sp. (Pl. 40, fig. 9).

Surface of the cortical shell thorny, covered with small spines. Both proximal chambers nearly kidney-shaped, with irregular, polygonal pores, three to four times as broad as the bars; five to six pores on the half meridian, nine to ten on the half equator of each chamber. Both distal chambers nearly hemispherical, with a circle of ten to twelve large square pores at their base; the other pores much smaller, irregular, roundish. Polar tubuli prismatic, with prominent edges, nearly half as long as the main axis, only one-fourth as broad as the equatorial constriction. Pores of the tubuli very small, in longitudinal series between the edges.

Dimensions.—Total length of the shell (without tubuli) 0.18 to 0.2, greatest breadth (in the equator of the proximal chambers) 0.07 to 0.09; pores 0.003 to 0.01, bars 0.002 to 0.004; length of the polar tubuli 0.06 to 0.09, breadth of them 0.015 to 0.02.

Habitat.—Pacific, central area, Stations 270 to 272, depth 2425 to 2925 fathoms.

Genus 168. Peripanarium,^[47] n. gen.

Definition.—Panartida with double cortical shell and double medullary shell, with two hollow fenestrated tubes, opposite on the poles of the main axis.

The genus Peripanarium differs from Panarium only in the development of an outer reticulated envelop, which mantle-like surrounds the shell and represents a second or external cortical shell. It bears therefore to Panarium the same relation as Peripanartus to Panartus, &c.

1. Peripanarium cenoconicum, n. sp.

Internal cortical shell with four kidney-shaped chambers of nearly the same form and size; their pores irregular, roundish, twice to four times as broad as the bars. External cortical shell cylindrical, hemispherical at both poles, with irregular, very small, roundish pores, only one-third to one-half as large as those of the internal. From both poles of the internal cortical shell arises a hollow conical fenestrated tube, which perforates the external. The outer free part of this slender cone equals in length the inner part or the distance between the two cortical shells, which is about equal to the length of one chamber. External surface covered with small thorns. (This species has the same appearance as Desmartus larvalis, Pl. 40, fig. 12, but has only four chambers instead of six.)

Dimensions.—Main axis (without cones) 0.23, greatest breadth 0.11; pores of the inner cortical shell 0.004 to 0.009, of the outer 0.002 to 0.003; bars of the former 0.002, of the latter 0.001; total length of the polar cones 0.05, basal thickness of them 0.03.

Habitat.—West Tropical Pacific, Station 225, depth 4475 fathoms.

2. Peripanarium cenocylindricum, n. sp.

Internal cortical shell with four unequal chambers, the two proximal kidney-shaped, the two distal conical, and somewhat smaller; pores irregular, polygonal-roundish, twice to five times as broad as the bars. External cortical shell nearly spindle-shaped, in the equatorial zone inflated, conical, tapering towards both poles, its pores very small, roundish, its surface covered with small thorns. The shell of this species resembles very much Peripanartus atractus (Pl. 40, fig. 7), but differs by the hollow cylindrical polar tubes, which arise from both poles of the inner cortical shell and attain more than half the length of the main axis. They are open at their ends (broken away), about as broad as the outer medullary shell, and perforated by irregular, roundish pores.

Dimensions.—Main axis (without polar tubes) 0.28, greatest breadth (in the equator) 0.16; pores of the inner cortical shell 0.004 to 0.01, of the outer 0.002 to 0.005; bars of the former 0.004, of the latter 0.002; total length of the polar tubes 0.16, breadth of them 0.03.

Habitat.—Pacific, central area, Station 268, depth 2900 fathoms.

Family XVII. Zygartida, Haeckel (Pl. 40, figs. 10-13).

Zygartida, Haeckel, 1881, Prodromus, p.462 (sensu restricto).

Definition.—Prunoidea with annulated cortical shell, the external shell being divided by five or more parallel transverse constrictions into six or more chambers, enclosing in the centre two internal concentric shells (medullary shells). Central capsule cylindrical, commonly annulated (corresponding to the transverse annular constrictions of the cortical shell).

The family Zygartida, the seventh and last of the Prunoidea, comprises, in the sense here restricted, all those Prunoidea in which the cortical shell is annulated and composed of six to twenty or more (at least six) cameræ, lying one behind another in the elongated main axis, and separated by five or more annular constrictions. When I constituted this family in 1881 (loc. cit.), I had given to it a much wider extent, embracing all those Prunoidea which exhibit annular constrictions of the cortical shell; as the number of these, in consequence of further researches, is much increased, it seems now more convenient to restrict the family to the extent here given.

No doubt the Zygartida must be derived from the Panartida by progressive growth of the cortical shell in the main axis and accompanying increase of the number of its chambers. Whilst this number in the Panartida is constantly restricted to four, in the Zygartida it amounts to ten, twenty, or more, and is in the lowest case six (Pl. 40, fig. 10). The maximum number is variable in the different species, but of course also different in the various degrees of individual development. Each Zygartid is at the beginning of its growth a Cyphinid, later a Panartid. The number of the annular constrictions separating the chambers and lying in parallel transverse planes is at least five, but may amount to nineteen, to twenty-one or more; they lie constantly in pairs on both sides of the equatorial constriction (Pl. 40, figs. 12, 13).

The cortical shell may either remain simple (Ommatocampe, Pl. 40, fig. 10), or become double (Desmocampe, Pl. 40, fig. 12), or sometimes triple (Zygocampe, (Pl. 40, fig. 13). In the latter cases the outer (secondary and tertiary) cortical shells are commonly incomplete, and only developed around the proximal chambers of the complete first (primary) cortical shell, its distal chambers remaining simple.

The Medullary Shell is constantly double, as in the Panartida; its form is either spherical or lenticular, compressed in the direction of the main axis. It is always connected with the equatorial constriction of the cortical shell by a number of radial beams, lying either in the equatorial plane or on each side of it (Pl. 40, figs. 10-13).

The Central Capsule of the Zygartida is constantly cylindrical; its increasing growth on both poles of the axis corresponds to that of the including cortical shell. Commonly (but not always) its cylindrical surface is annulated, with five or more transverse strictures, corresponding to those of the cortical shell. From the inner surface of the latter it is separated by a jelly-mantle, the calymma.

Synopsis of the Genera of Zygartida.

III. Ommacampida. 1. Cortical shell simple. (Medullary shell double.)	$\scriptstyle {\left\{{\begin{matrix}\ \\\\\ \ \end{matrix}}\right.}$	Without polar tubes,	169. Ommatocampe.
		With two hollow fenestrated tubes, on the poles of the axis,	170. Ommatartus.
III. Desmocampida. 2. Cortical shell double. (Medullary shell double.)	$\scriptstyle {\left\{{\begin{matrix}\ \\\\\ \ \end{matrix}}\right.}$	Without polar tubes,	171. Desmocampe.
		With two hollow fenestrated tubes, on the poles of the axis,	172. Desmartus.
III. Zygocampida. 3. Cortical shell triple. (Medullary shell double.)	$\scriptstyle {\left\{{\begin{matrix}\ \\\\\ \ \end{matrix}}\right.}$	Without polar tubes,	173. Zygocampe.
		With two hollow fenestrated tubes, on the poles of the axis,	174. Zygartus.

Genus 169. Ommatocampe,^[48] Ehrenberg, 1860, Monatsber. d. k. preuss. Akad. d. Wiss. Berlin, p. 832.

Definition.—Zygartida with simple cortical shell and double medullary shell, without polar tubes.

The genus Ommatocampe was founded by Ehrenberg in 1860 for one of his "Haliommatina," with the following diagnosis:—"Shell rod-like, long, articulate, with nucleus, without spines, with four or more joints." The species figured by him, Ommatocampe polyarthra, exhibits five pairs of chambers on both sides of the meridian plane of the cortical shell, the centre of which includes a double medullary shell. It represents the most simple form of all Zygartida, and may be derived phylogenetically from Cyphonium simply by multiplication of the chambers of the cortical shell, growing on both poles of the main axis.

Subgenus 1. Ommatocampium.

Definition.—Surface of the cortical shell smooth or rough, without thorns or spines, also without polar spines.

1. Ommatocampe polyarthra, Ehrenberg.

Ommatocampe polyarthra, Ehrenberg, 1872, Abhandl. d. k. Akad. d. Wiss. Berlin, p. 279, Taf. vi. fig. 9.

Cortical shell with smooth surface, composed of six to ten chambers of the same size and form. Every chamber kidney-shaped, about twice as broad as long, with three transverse rows of circular, subregular pores, twice to three times as broad as the bars. Both medullary shells spherical.

Dimensions.—Length of the six-chambered cortical shell 0.15; greatest breadth of each chamber 0.04; pores 0.005 to 0.007, bars 0.002 to 0.003.

Habitat.—Californian Sea, depth 2600 fathoms, Ehrenberg; Pacific, central area, Station 268, depth 2900 fathoms; fossil in the Tertiary rocks of Barbados, Haeckel.

2. Ommatocampe increscens, Stöhr.

Ommatocampe increscens, Stöhr, 1880, Palæontogr., vol. xxvi. p. 90, Taf. ii. fig 2, a, b.

Cortical shell with rough surface, composed of six to ten chambers of nearly the same size and form; the breadth of the chambers a little increasing towards both poles. Every chamber kidney-shaped, the proximal chambers twice as broad as long, with four or five transverse rows of pores; the distal chambers three to four times as broad as long, with two or three transverse rows of pores. Form of the pores irregular, roundish, bars between them in the distal part smaller, in the proximal part larger than the pores. Both medullary shells compressed lenticular.

Dimensions.—Length of the six-chambered cortical shell 0.22; greatest breadth of the chambers 0.09 to 0.1; pores and bars 0.003 to 0.006.

Habitat.—Fossil in the Tertiary rocks of Sicily, Grotte, Stöhr.

3. Ommatocampe annulata, n. sp.

Cortical shell with smooth surface, composed of six to twelve chambers of nearly the same size and form. Each chamber kidney-shaped, twice as broad as long, with four to five transverse rows of irregular, roundish pores, once to five times as broad as the bars. On the base of each distal chamber (beginning in the second or third pair) a circle of twelve to sixteen larger square pores. Both medullary shells compressed lenticular. (Resembles the inner cortical shell of Desmartus larvalis, Pl. 40, fig. 12, but is without the polar tubes and the outer envelope of this species.)

Dimensions.—Length of the six-chambered cortical shell 0.23; greatest breadth of each chamber 0.07; pores 0.002 to 0.01, bars 0.002.

Habitat.—Cosmopolitan; Mediterranean, Atlantic, Pacific, in various depths.

Subgenus 2. Ommatocampula, Haeckel.

Definition.—Surface of the cortical shell thorny or spiny, but without peculiar polar spines and without regular coronals of spines.

4. Ommatocampe erucæformis, n. sp.

Cortical shell with spiny surface, composed of six to twelve chambers of nearly the same size and form, the distal chambers a little smaller. The form and structure of the cortical shell is nearly the same as in the foregoing species, only the pores are somewhat larger, and the whole surface is covered with bristle-like radial spines, about half as long as the breadth of one chamber. Both medullary shells compressed and lenticular.

Dimensions.—Length of the six-chambered cortical shell 0.24; greatest breadth of each chamber 0.08; pores 0.005 to 0.012, bars 0.002.

Habitat.—North Atlantic, Canary Islands, Station 353, depth 2965 fathoms.

5. Ommatocampe nereis, n. sp. (Pl. 40, fig. 10).

Cortical shell with spiny surface, composed of six (or more) chambers of different size and structure. Both proximal chambers kidney-shaped, with subregular, circular, hexagonally framed pores, twice as broad as the bars. All following chambers cap-like, with much smaller, irregular, roundish pores, at the base of every chamber a circle of ten to twelve large square pores. Spines of the surface short, irregularly scattered. Both medullary shells spherical. (All the observed specimens possessed only six chambers.)

Dimensions.—Length of the six-chambered cortical shell 0.25; greatest breadth of each chamber 0.08; pores of both proximal chambers 0.01, bars 0.005; basal pores of the other chambers 0.02; pores of their distal caps 0.003 to 0.006, bars 0.003.

Habitat.—Pacific, central area, Stations 271 to 274, depth 2350 to 2750 fathoms.

Subgenus 3. Ommatocorona, Haeckel.

Definition.—Surface of the cortical shell spiny, on every chamber a regular circle or coronal of radial spines.

6. Ommatocampe chætopodum, n. sp.

Cortical shell with spiny surface, composed of six (or more) kidney-shaped chambers of different size and form. Both proximal chambers kidney-shaped, with subregular, circular, hexagonally framed pores, about as broad as the bars. All the following chambers hemispherical, with irregular, roundish pores; at the base of every chamber a circle of ten to twelve larger square pores. The beams between these latter are prolonged into free radial spines, twice as thick as the bars. Therefore every chamber is surrounded by a circle of radial spines, like those of Panicium coronatum (Pl. 40, fig. 4). Both medullary shells lenticular.

Dimensions.—Length of the six-chambered cortical shell 0.3, greatest breadth 0.08, pores and bars of both proximal chambers 0.01; pores of the other chambers 0.002 to 0.008; square pores 0.02, bars 0.005; length of the coronal spines 0.03, thickness 0.01.

Habitat.—Indian Ocean, Madagascar, Rabbe.

Subgenus 4. Ommatacantha, Haeckel.

Definition.—Surface of the shell smooth or spiny, on the poles of the main axis occur two strong opposite polar spines.

7. Ommatocampe amphilonche, n. sp.

Cortical shell composed of six kidney-shaped chambers of nearly the same size and structure; every chamber twice as broad as long, with four to five transverse rows of irregular, roundish pores, once to four times as broad as the bars. Both medullary shells lenticular. Surface of the cortical shell covered with bristle-like spines. On both poles of the main axis one larger, strong, conical spine, about half as long as this axis, and on the base as broad as the inner medullary shell. (Resembles on the whole Desmartus larvalis, Pl. 40, fig. 12, but without external mantle, and with two solid polar spines instead of the polar tubes.)

Dimensions.—Length of the six-chambered cortical shell 0.24; greatest breadth of each chamber 0.08; pores 0.002 to 0.08, bars 0.002; length of the polar spines 0.12, basal thickness 0.02.

Habitat.—Pacific, central area, Station 266, depth 2750 fathoms.

Genus 170. Ommatartus,^[49] Haeckel, 1881, Prodromus, p. 463.

Definition.—Zygartida with simple cortical shell and double medullary shell, with two hollow fenestrated tubes, opposite on both poles of the main axis.

The genus Ommatartus differs from Ommatocampe by the development of two hollow fenestrated tubes on both poles of the main axis, and bears therefore the same relation to it as Cannartidium to Cyphonium. The former two genera differ from the two latter by the augmentation of the chambers of the cortical shell.

1. Ommatartus amphicanna, n. sp.

Cortical shell with spiny surface, composed of six chambers of equal size and kidney-shaped; every chamber with four to five transverse rows of irregular, roundish pores, twice to three times as broad as the bars. Both medullary shells lenticular. Polar tubes conical, about as long as one chamber, with smaller pores. Both medullary shells spheroidal, more or less compressed. (Resembles Desmartus larvalis, Pl. 40, fig. 12, but is without the external shell.)

Dimensions.—Length of the six-chambered cortical shell 0.24; greatest breadth of each chamber 0.07; pores 0.008 to 0.012, bars 0.004; length of the polar tubes 0.04 to 0.05, basal thickness 0.02.

Habitat.—Pacific, central area, Stations 270 to 274, depth 2350 to 2925 fathoms.

2. Ommatartus amphisiphon, n. sp.

Cortical shell with spiny surface, composed of six or eight chambers of different size and form. Both proximal chambers kidney-shaped, each with five to six transverse rows of irregular, polygonal pores, three to four times as broad as the bars. The other (four to six) chambers somewhat smaller, more hemispherical, with smaller, irregular pores, but on the base of each a circle of ten to twelve larger square pores. Polar tubuli prismatic, about half as long as the main axis, with prominent edges and longitudinal rows of smaller pores between them. Both medullary shells lenticular. (Resembles closely Panarium tubularium, Pl. 40, fig. 9, but with six to eight chambers instead of four, and with longer tubuli.)

Dimensions.—Length of the six-chambered cortical shell 0.26; greatest breadth of the proximal chambers 0.09, of the distal chambers 0.07; pores of the former 0.01, of the latter 0.004; large square pores 0.013, bars 0.003; length of the polar tubes 0.1 to 0.12, thickness 0.02.

Habitat.—South Pacific, Station 297, depth 1775 fathoms.

3. Ommatartus amphobolus, n. sp.

Cortical shell with spiny surface, composed of six chambers of different size and form. Both proximal chambers kidney-shaped, with four to five transverse rows of subregular, circular pores, twice as broad as the bars. Both middle chambers cap-like, with a basal circle of ten to twelve larger square pores, and small roundish pores on the cap. Both distal chambers smaller, conical, with very small roundish pores. Polar tubuli conical, nearly half as long as the main axis, also with very small pores. Both medullary shells lenticular.

Dimensions.—Length of the six-chambered shell 0.28, greatest breadth 0.08; pores of the proximal chambers 0.01, bars 0.005; pores of the distal chambers and the polar tubes 0.002 to 0.004, bars 0.002; length of the polar tubes 0.13, basal thickness 0.03.

Habitat.—North Pacific, Station 253, depth 3125 fathoms.

Genus 171. Desmocampe,^[50] n. gen.

Definition.—Zygartida with double cortical shell and double medullary shell, without polar tubes.

The genus Desmocampe differs from Ommatocampe in the duplication of the jointed cortical shell; the radial spines, which start from the surface of the inner cortical shell, are connected one with another by transverse communicating branches which form an outer envelop around it; but this reticulated mantle is commonly not quite perfect and more or less irregular.

1. Desmocampe catenula, n. sp.

Inner cortical shell with six to eight chambers of the same size and form. Every chamber kidney-shaped, with three to four transverse rows of circular, subregular pores, twice as broad as the bars. Outer cortical shell cylindrical, hemispherical at both poles, with smooth surface and irregular, roundish pores of very different size. Distance between the two cortical shells equals the diameter of the outer medullary shell, which, like the inner, is spherical. (Resembles Ommatocampe polyarthra, Ehrenberg, 1872, loc. cit., Taf. vi, fig. 9, but differs in the external mantle.)

Dimensions.—Length of the six-chambered inner cortical shell 0.16, of the outer 0.21; greatest breadth of each chamber of the former 0.05, of the latter 0.09; pores of the inner 0.006, bars 0.003; pores of the outer 0.002 to 0.008, bars 0.002.

Habitat.—North Pacific, Station 237, off Japan, surface.

2. Desmocampe tænioides, n. sp.

Inner cortical shell with six to ten chambers of nearly the same size and form; the distal chambers somewhat smaller. Every chamber kidney-shaped, with four to five transverse rows of irregular roundish pores, twice to three times as broad as the bars. Outer cortical shell cylindrical, hemispherical at both poles, with spiny surface; its pores like those of the inner, but the bars between them much thinner. Distance between the two cortical shells equals the diameter of the outer medullary shell. Both medullary shells lenticular. (Resembles Desmartus larvalis, Pl. 40, fig. 12, but is without polar tubes.)

Dimensions.—Length of the six-chambered inner cortical shell 0.25, of the outer 0.3; greatest breadth of the former 0.07, of the latter 0.11; pores 0.005 to 0.012; bars of the inner shell 0.004, of the outer 0.001.

Habitat.—Pacific, central area, Station 268, depth 2900 fathoms.

3. Desmocampe aphrodite, n. sp.

Inner cortical shell with six to ten chambers of different size and structure. Both proximal chambers kidney-shaped, with five to six transverse rows of subregular, circular, hexagonally-framed pores, twice as broad as the bars. All following chambers cap-like, with much smaller, irregular, roundish pores, on the base of each a circle of ten to twelve large square pores. Outer cortical shell cylindrical, on both poles hemispherical, with spiny surface and very delicate network of small polygonal pores. Both medullary shells spherical. (The inner cortical shell of this species resembles that of Ommatocampe nereis, Pl. 40, fig. 10; the outer that of Cyphocolpus virginis, Pl. 40, fig. 11.)

Dimensions.—Length of the six-chambered internal cortical shell 0.25, of the outer 0.3; greatest breadth of the former 0.08, of the latter 0.12; pores of the proximal chambers of the inner shell 0.01, bars 0.005; pores of the distal chambers 0.003 to 0.005, square pores 0.02, bars 0.003; pores of the external cortical shell 0.002 to 0.006, bars 0.001.

Habitat.—North Atlantic, Station 353, depth 2965 fathoms.

4. Desmocampe atractus, n. sp.

Inner cortical shell with six chambers of very different size and structure. Both proximal chambers kidney-shaped, with seven to eight transverse rows of subregular, roundish pores, twice to three times as broad as the bars. Both middle chambers cap-like, on the base with a circle of eight to ten very large square pores, on the distal cap with small irregular, roundish pores. Both distal chambers conical, also with small irregular, roundish pores. Outer cortical shell spindle-shaped, inflated in the equatorial zone, tapering conically towards both poles, with very delicate network of small roundish pores and thin bars. Surface covered with innumerable very small spines. Both medullary shells lenticular. (Resembles very much Peripanartus atractus, Pl. 40, fig. 7, but differs in the number of the chambers and their proportion to the outer mantle, which envelops spindle-like all six chambers.)

Dimensions.—Length of the six-chambered internal cortical shell 0.27, of the outer 0.32; greatest breadth of the former 0.09, of the latter 0.15; pores of the inner cortical shell (on an average)—proximal chambers 0.008, middle chambers 0.02, distal chambers 0.004, bars 0.004; pores of the outer cortical shell 0.002 to 0.004, bars 0.002.

Habitat.—North Pacific, Station 241, depth 2300 fathoms.

Genus 172. Desmartus,^[51] n. gen.

Definition.—Zygartida with double cortical shell and double medullary shell, with two hollow fenestrated tubes, opposite on both poles of the main axis.

The genus Desmartus differs from Desmocampe by the development of two hollow fenestrated tubes, opposite on both poles of the main axis, and bears therefore the same relation to it as Ommatartus to Ommatocampe. Both the former genera can be produced from the two latter by duplication of the cortical shell.

1. Desmartus larvalis, n. sp. (Pl. 40, fig. 12).

Zygartus larvalis, Haeckel, 1881, Prodromus et Atlas (pl. xl, fig. 12).

Inner cortical shell composed of six kidney-shaped chambers of nearly the same size and structure; every chamber twice as broad as long, with four to five transverse rows of irregular, roundish pores, twice to five times as broad as the bars; the basal pores of the distal chambers somewhat larger and more square. Outer cortical shell cylindrical, hemispherical at both poles, with irregular, polygonal pores, on an average twice as large as those of the inner, but the bars between them much thinner. Outer surface spiny. Both medullary shells lenticular. Polar tubes conical, a little longer than one internal chamber, as broad at the base as the inner medullary shell. Sometimes the tubes exhibit prominent edges (as in the lower spine of fig. 12); the pores of these are very small, and roundish.

Dimensions.—Length of the six-chambered internal cortical shell 0.23, of the external 0.3; greatest breadth of the former 0.07, of the latter 0.11; pores of the inner shell 0.004 to 0.01, of the outer 0.01 to 0.02; bars of the former 0.002, of the latter 0.001; length of the polar tubes 0.05, basal thickness 0.02.

Habitat.—North Pacific, Station 241, depth 2300 fathoms.

2. Desmartus tubulatus, n. sp.

Inner cortical shell composed of six to ten kidney-shaped chambers, tapering in size towards both poles, every chamber with six to seven transverse rows of irregular, roundish pores, twice to six times broader than the bars. Outer cortical shell spindle-shaped, in the equatorial zone inflated, tapering towards both poles, its network similar to the inner, only more delicate. Polar tubes conical, twice as long as an inner chamber, as broad at the base as the outer medullary shell. Both medullary shells lenticular.

Dimensions.—Length of the six-chambered internal cortical shell 0.25, of the external 0.32; greatest breadth of the former 0.08, of the latter 0.12; pores of the inner shell 0.002 to 0.012, of the outer 0.003 to 0.01; bars of the former 0.002, of the latter 0.001; length of the polar tubes 0.07, basal thickness 0.03.

Habitat.—North Pacific, Station 256, depth 2950 fathoms.

Genus 173. Zygocampe,^[52] n. gen.

Definition.—Zygartida with triple (or multiple) cortical shell and double medullary shell, without polar tubes.

The genus Zygocampe differs from Desmocampe and Ommatocampe by the multiplication of the cortical shell, which is composed of three or more concentric envelopes. The three mentioned genera form therefore a phylogenetic series, produced by the concentric increase on the outside of the jointed cortical shell. Commonly the second cortical shell is not as complete as the first (or innermost), and the third (or outermost) is yet more incomplete. Rarely the number of the concentric cortical shells surpasses three.

1. Zygocampe pupula, n. sp.

Inner cortical shell with six to twelve chambers of nearly the same size and form. Every chamber kidney-shaped, with four to five transverse rows of circular, subregular pores, twice as broad as the bars. Middle cortical shell cylindrical, hemispherical at both poles, with subregular circular pores somewhat smaller than those of the inner; the bars also thinner. Outer cortical shell of the same form as the middle, but with very delicate network, and quite irregular, roundish pores and very thin bars. Surface quite smooth. Both medullary shells lenticular. (May be regarded in a phylogenetic as well as an ontogenetic sense, as the further developmental form of Desmocampe catenula and Ommatocampe polyarthra.)

Dimensions.—Length of the six-chambered inner cortical shell 0.17, of the middle 0.22, of the outer 0.27; greatest breadth of the first 0.05, of the second 0.09, of the third 0.12; pores of the inner cortical shell 0.005, of the middle 0.004, of the outer 0.003 to 0.012; bars of the first 0.003, of the second 0.002, of the third 0.001.

Habitat.—Pacific, central area, Station 266, depth 2750 fathoms.

2. Zygocampe corasium, n. sp.

Inner cortical shell with six to eight chambers of different size and form. Both proximal chambers kidney-shaped, with five to six transverse rows of subregular, circular, hexagonally framed pores, twice as broad as the bars. All following chambers cap-like, the distal somewhat smaller; their pores much smaller, irregular, roundish; only at the base of each chamber a circle of ten to twelve large square pores. Middle cortical shell cylindrical, in the equatorial zone a little constricted, hemispherical at both poles, with irregular delicate network of roundish, polygonal meshes. Outer cortical shell of the same form as the middle, but with a very delicate and quite irregular network of polygonal meshes. Commonly this outer mantle is incomplete, and sometimes interwoven in a spongy manner with the middle (or also with the inner). Surface covered with many irregular, thin, bristle-like spines. Both medullary shells lenticular. (May be considered in a phylogenetic and ontogenetic sense as a further developmental stage of Desmocampe aphrodite and Ommatocampe nereis, Pl. 40, fig. 10.)

Dimensions.—Length of the six-chambered inner cortical shell 0.24, of the middle 0.3, of the outer 0.36; greatest breadth of the first 0.08, of the second 0.12, of the third 0.16, pores of the first (on an average) 0.005 to 0.02, of the second 0.003 to 0.015, of the third 0.01 to 0.05; bars corresponding 0.005 or 0.003 or 0.001.

Habitat.—North Pacific, Station 253, depth 3125 fathoms.

3. Zygocampe chrysalidium, n. sp. (Pl. 40, fig. 13).

Inner cortical shell with six to eighteen chambers of different size and form. Both proximal chambers kidney-shaped, with six to seven transverse rows of subregular, circular pores, three to four times as broad as the bars. All following chambers with more irregular pores, with a circle of ten to twelve larger square pores at the base. Middle cortical shell with smaller, irregular, roundish pores. Outer cortical shell with larger polygonal, quite irregular pores. Both outer shells appear commonly incomplete or somewhat irregularly developed, and sometimes in a spongy manner interwoven with one another. Surface covered with irregular, bristle-like spines. Both medullary shells spherical. The breadth of the chambers decreases gradually towards both poles, so that the whole shell assumes a spindle form. Sometimes on both poles is developed a short conical polar tube (in fig. 13 only on the upper pole), and so this species is transformed into Zygartus chrysalis.

Dimensions.—Length of the six-chambered inner cortical shell 0.25, of the middle 0.3, of the outer 0.35; greatest breadth of the first 0.07, of the second 0.11, of the third 0.14; pores (on an average) 0.01 (0.002 to 0.02), bars 0.002 to 0.005.

Habitat.—Pacific, central area, Stations 272 to 274, depth 2350 to 2750 fathoms.

Genus 174. Zygartus,^[53] Haeckel, 1881, Prodromus, p. 463.

Definition.—Zygartida with triple (or multiple) cortical shell and double medullary shell, with two hollow fenestrated tubes, opposite on both poles of the main axis.

The genus Zygartus differs from Zygocampe by the development of two hollow fenestrated tubes, on the two opposite poles of the main axis. It exhibits therefore to the latter the same relation that Desmartus does to Desmocampe and Ommatartus to Ommatocampe; it differs from these by the multiplication of the cortical shell, which is composed of at least three concentric envelopes.

1. Zygartus doliolum, n. sp.

Inner cortical shell composed of six (or more) kidney-shaped chambers, all nearly of the same size and structure, every chamber with four to five transverse rows of irregular, roundish pores, twice to four times as broad as the bars; the basal pores scarcely larger than the apical pores. Middle cortical shell nearly of the same structure as the inner, only the pores larger and the bars thinner. Outer cortical shell cylindrical, hemispherical at both poles, its network very delicate, with large irregular, polygonal pores, and very thin bars between them; its surface covered with thin bristle-like spines. Both medullary shells lenticular. Polar tube cylindrical, with conical apex, and with very small pores; its length equals the breadth of two internal chambers, its breadth that of the inner medullary shell. (This species appears to be a further developed form of Ommatocampe annulata and Desmartus larvalis, Pl. 40, fig. 12.)

Dimensions.—Length of the six-chambered inner cortical shell 0.25, of the middle 0.3, of the outer 0.35; greatest breadth of the first 0.07, of the second 0.11, of the third 0.15; pores of the inner shell 0.005 to 0.01, of the middle 0.003 to 0.007, of the outer 0.008 to 0.02; bars of the first 0.002, of the second and third 0.001; length of the polar tubes 0.15, basal thickness 0.02.

Habitat.—Pacific, central area, Station 270, depth 2925 fathoms.

2. Zygartus chrysalis, n. sp. (Pl. 40, fig. 13).

Inner cortical shell composed of six to twenty (commonly eight to twelve) chambers of different size and form. Both proximal chambers nearly hemispherical, with spiny surface and subregular, circular pores, three to four times as broad as the bars. All following chambers cap-like, tapering towards both poles, with more irregular, roundish pores, with a circle of ten to twelve larger square pores at the base. Middle cortical shell with smaller roundish pores. Outer cortical shell with larger polygonal, quite irregular pores. Both medullary shells lenticular. Polar tubes conical or cylindrical with conical apex, of very variable length, sometimes not longer than one internal chamber, at other times twice to four times as long (in the figured specimen not fully developed, as also a part of the shells). Differs from Zygocampe chrysalis only by the production of polar tubes.

Dimensions.—Length of the six-chambered inner cortical shell 0.25, of the middle 0.3, of the outer 0.35; greatest breadth of the first 0.07, of the second 0.11, of the third 0.14; other measures the same as in Zygocampe chrysalis; length of the tubes 0.05 to 0.12 or more.

Habitat.—Pacific, central area, Stations 270 to 274, depth 2350 to 2925 fathoms.

1. Cenellipsis = Hollow ellipsoid; κενός, ἔλλειψις.
2. Axellipsis = Ellipsoid with an axial beam; ἄξις, ἔλλειψις.
3. Ellipsidium = Small ellipsoid; ἐλλειψίδιον.
4. Ellipsoxiphus = Ellipsoid with swords; ἔλλειψις, ξίφος.
5. Axoprunum = Plum with axis; ἄξις, προῦνον.
6. Ellipsostylus = Ellipsoid with styles; ἔλλειψις, στῦλος.
7. Lithomespilus = Siliceous medlar; λίθος, μέσπιλος.
8. Lithapium = Siliceous pear; λίθος, ἄπιον.
9. Pipettella = Small pipette.
10. Druppula = Small drupe or δρύππα, ripe Olive.
11. Druppocarpus = Olive-fruit; δρύππα, κάρπος.
12. Prunulum = Little-plum.
13. Prunocarpus = Plum fruit; προῦνον, κάρπος.
14. Cromyodruppa = Onion-olive; κρόμυον, δρύππα.
15. Cromyocarpus = Onion fruit; κρόμυον, κάρπος.
16. Lithatractus = Spindle of silex; λίθος, ἄτρακτος.
17. Druppatractus = Spindle-like olive; δρύππα, ἄτρακτος.
18. Stylatractus = Spindle with styles; στῦλος, ἄτρακτος.
19. Xiphatractus = Sword-spindle; ξίφος, ἄτρακτος.
20. Cromyatractus = Onion-spindle; κρόμυον, ἄτρακτος.
21. Pipetta = Small pipe.
22. Pipettaria = Pipetta-like.
23. Spongellipsis = Spongy ellipsoid; σπόγγος, ἔλλειψις.
24. Spongurus = Spongy tail; σπόγγος, ὀυρά.
25. Spongocore = Spongy puppet; σπόγγος, κόρη.
26. Spongoprunum = Spongy plum; σπόγγος, προῦνον.
27. Spongodruppa = Spongy olive-fruit; σπόγγος, δρύππα.
28. Spongatractus = Spongy-spindle; σπόγγος, ἄτρακτος.
29. Spongoliva = Spongy olive; σπόγγος, ἐλειά.
30. Spongoxiphus = Spongy sword; σπόγγος, ξίφος.
31. Artiscus = Small loaf; ἀρτίσκος.
32. Stylartus = Bread with styles; στῦλος, ἄρτος.
33. Cannartus = Leaf with tubes; κάννα, ἄρτος.
34. Cyphanta = Κύφαντα, Mediterranean port in Laconia.
35. Cyphonium = Roundish vessel; κύφωνιον.
36. Cypassis = κυπασσίς; A girl's girdle.
37. Cyphocolpus = Vaulted-bosom; κύφος, κόλπος.
38. Cyphinus = κύφινος; derivation from κύφος = roundish vessel, a kind of fruit.
39. Cyphinidium = Small Cyphinus; κυφινίδιον.
40. Cannartiscus = Small loaf with tubes; κάννα, ἀρτίσκος.
41. Cannartidium = Small loaf with tubules; κάννα, ἀρτίδιον.
42. Panartus = quite bread-like; πάναρτος.
43. Peripanartus = Panartus with mantle; περιπάναρτος.
44. Panicium = A kind of bread.
45. Peripanicium = Panicium with mantle.
46. Panarium = Bread-basket.
47. Peripanarium = Panarium (or bread-basket) with mantle.
48. Ommatocampe = Caterpillar with eyes; ὄμμα, κάμπη.
49. Ommatartus = Loaf with eyes; ὄμμα, ἄρτος.
50. Desmocampe = Chain-like caterpillar; δεσμός, κάμπη.
51. Desmartus = Chain-like loaf; δεσμός, ἄρτος.
52. Zygocampe = Caterpillar with paired joints; ζυγόν, κάμπη.
53. Zygartus = Loaf with paired joints; ζυγόν, ἄρτος.