Report on the Radiolaria/Prunophracta
Suborder II. PRUNOPHRACTA.
Definition.—Shell ellipsoidal, lenticular or diploconical, with radial beams of different size.
Definition.—Acantharia with a simple ellipsoidal lattice-shell, composed of the branched apophyses of twenty radial spines meeting in its centre and disposed according to the Müllerian law of Icosacantha. Two opposite equatorial spines larger than the two others. Central capsule ellipsoidal, enclosed in the fenestrated shell.
The family Belonaspida, formerly united by me with the Dorataspida (in the Prodromus, 1881, p. 468), differs from it in the ellipsoidal form of the lattice-shell and the enclosed central capsule. In the spherical Dorataspida, their ancestral family, all twenty radial spines are of equal size, whilst here in the Belonaspida two opposite spines are larger than the eighteen others. These two larger or principal spines are both equatorial spines, placed in the longitudinal or major axis of the ellipsoid, or the "hydrotomical axis" (compare above, p. 719). The two other equatorial spines are constantly smaller, and lie in the transverse or minor axis of the ellipsoid, or the "geotomical axis." The geometrical proportion of these two determining axes of the ellipsoidal shell is very variable (even in one and the same species), commonly 4 : 3 or 3 : 2, rarely 2 : 1, often only 5 : 4 or 6 : 5. All meridian planes, passing through the principal spines (or the longitudinal axis of the shell) are elliptical, and of equal size. All transverse planes, perpendicular to that axis, are circular; the largest of these circular parallel planes is the geotomical plane, which passes through the smaller equatorial spines and the spineless axis.
In the spherical Dorataspida the internal length of the radial spines (or the distance between the shell and the centre) is equal in all twenty spines. In the ellipsoidal Belonaspida this internal length is different, and commonly exhibits four different degrees; in the two principal spines it is of first rank, in the eight tropical spines of second rank, in the four (hydrotomical) polar spines of third rank, and in the six spines (four geotomical polar spines and two transverse equatorial spines) of fourth rank. These differences of the internal length become more important the more the hydrotomical axis is prolonged. Regarding all other qualities (in form, disposition, and mode of junction at the centre) the ellipsoidal Belonaspida do not differ from their ancestral group, the spherical Dorataspida (compare above, p. 802). In both families the pyramidal central bases of the twenty spines are commonly supported one upon another with their triangular neighbouring faces; but sometimes also here (particularly in Phatnaspis) the central bases are perfectly grown together. In this case also the sutures of the meeting branches of the apophyses are obliterated, whilst usually they remain open. Such forms, with spines and plates perfectly grown together, form a single piece of acanthin, and were formerly separated by me as a peculiar genus Haliommatidium (Monogr. d. Radiol., 1862, p. 419). But as I now find this concrescence to be an accidental and inconstant peculiarity of some species, it no longer seems to me to be of generic importance.
The apophyses of the twenty radial spines, the branches of which compose the ellipsoidal lattice-shell, exhibit in all Belonaspida the same appearance as in the Diporaspida (and especially the Ceriaspida) among the spherical Dorataspida. Everywhere each radial spine gives off only two opposite primary apophyses, the fork-branches of which unite together and form a plate or shield with two aspinal pores (as in Dorataspis). Commonly the shell exhibits only these forty parmal pores, the other meshes between them being sutural pores. Only in one genus, Phatnaspis (Pl. 136, figs. 6-9), is this number multiplied; the two opposite primary apophyses are here crossed by numerous perpendicular lateral branches, and these are again united by secondary perpendicular ramules which are parallel to the apophyses themselves; therefore each plate here forms a rhombic shield pierced by very numerous (often more than one hundred) small quadrangular or circular pores. Only two of these numerous parmal pores are the primary aspinal pores (sometimes, as in Pl. 136, fig 8, distinguished by their larger size); all others are secondary or coronal pores. Therefore Phatnaspis repeats the characteristic formation of Coscinaspis, from which it differs in its ellipsoidal shell.
Moreover, the four other genera of the ellipsoidal Belonaspida correspond perfectly to certain genera of the spherical Dorataspida, and may be derived from these by hypertrophy or stronger development of two opposite equatorial spines. In Thoracaspis and Belonaspis (Pl. 139, figs. 8, 9) the surface of the shell-plates is without crests and dimples (in the former without, in the latter with accessory by-spines); they thus correspond to Dorataspis and Diporaspis among the Dorataspida. In two other genera the surface of the shell-plates bears a network of elevated crests, separating funnel-shaped dimples, in Dictyaspis without, in Coleaspis with by-spines; these correspond to Ceriaspis and Hystrichaspis among the Dorataspida. The small by-spines, covering the surface, exhibit the same forms as in the Dorataspida; but they are usually smaller, and less developed in the Belonaspida.
The twenty radial spines are commonly more or less compressed or two-edged, sometimes very flat, broad, and triangular (Pl. 139, figs. 8, 9). In some species (mainly of Phatnaspis) they are very long, thin, and needle-shaped (Monogr. d. Radiol., 1862, Taf. xxii. figs. 10-12). Rarely they are cylindrical, four-edged, or prismatic. The Belonaspida testify by this and other peculiarities to their near relation to the Diporaspida and Phractacanthida and their older origin from Zygacantha.
The Central Capsule is in the Belonaspida ellipsoidal, and more or less prolonged in the hydrotomical or longitudinal axis of the shell. It is constantly smaller than the enveloping ellipsoidal shell, and separated from it by the calymma. Its structure and the shape of its nucleus are the same as in the nearly allied Dorataspida.
Synopsis of the Genera of Belonaspida.
| I. Subfamily Coleaspida.
Forty parmal pores (two aspinal pores on each plate, no coronal pores). |
Plates not dimpled, without prominent crests. | No by-spines, | 371. Thoracaspis. | ||
| With by-spines, | 372. Belonaspis. | ||||
| Plates dimpled, with a network of prominent crests, | No by-spines, | 373. Dictyaspis. | |||
| With by-spines, | 374. Coleaspis. | ||||
| II. Subfamily Phatnaspida.
Eighty to two thousand or more parmal pores (two aspinal pores on each plate, surrounded by two to one hundred or more coronal pores). |
No by-spines (plates not dimpled), | 375. Phatnaspis. | |||
Genus 371. Thoracaspis,[1] Haeckel, 1862, Prodromus, p. 468.
Definition.—Belonaspida with forty parmal pores (two on each plate), without dimples and crests, also without by-spines, therefore with smooth surface.
The genus Thoracaspis is the simplest form among the Belonaspida, and repeats in this family the nearly allied genus Dorataspis among the Dorataspida. It differs from this genus only in the characteristic prolongation of one equatorial axis, which effects an ellipsoidal transformation of the spherical central capsule and the enclosing lattice-shell.
1. Thoracaspis ellipsoides, n. sp.
Parmal pores large, elliptical, five or six times as large as the small circular sutural pores. Each plate surrounded by five or six sutural pores (a single one on each side). Spines compressed triangular, sword-like, two-edged; inner and outer half of nearly equal length.
Dimensions.—Length of the ellipsoidal shell (or major axis) 0.15, breadth (or minor axis) 0.12; length of the spines 0.07, basal breadth 0.016.
Habitat.—North Pacific, Station 253, surface.
2. Thoracaspis nephropora, n. sp.
Parmal pores large, kidney-shaped, three to four times as large as the roundish small sutural pores. Each plate surrounded by five or six sutural pores (a single one on each side). Spines in the inner longer part cylindrical, in the outer shorter part conical, not compressed.
Dimensions.—Length of the shell 0.2, breadth 0.15; length of the spines 0.06, basal breadth 0.018.
Habitat.—Central Pacific, Station 268, surface.
3. Thoracaspis circopora, n. sp.
Parmal pores circular, of the same size as the circular sutural pores. Each plate surrounded by five or six sutural pores (a single one on each side). Spines compressed, thin, linear, two-edged; outer part one and a half times as long as the inner.
Dimensions.—Length of the shell 0.17, breadth 0.13; length of the spines 0.12, basal breadth 0.003.
Habitat.—South Pacific, Station 288, surface.
4. Thoracaspis bipennis, n. sp. (Pl. 139, fig. 8).
Parmal pores elliptical, about twice as large as the circular sutural pores, which are of rather variable size. Each plate surrounded by eight to twelve sutural pores (commonly two on each side). Spines compressed, triangular, gradually tapering towards both ends; outer half a little longer, and much broader than the inner.
Dimensions.—Length of the shell 0.14, breadth 0.12; length of the spines 0.08, basal breadth 0.025.
Habitat.—Central Pacific, Station 274, surface.
Genus 372. Belonaspis,[2] Haeckel, 1862, Prodromus, p. 468.
Definition.—Belonaspida with forty parmal pores (two on each plate), without dimples and crests, but with numerous by-spines on the surface.
The genus Belonaspis differs from its ancestral genus Thoracaspis only in the possession of numerous superficial by-spines, and bears therefore to it the same relation as Diporaspis does to Dorataspis. The two latter differ from the two former in the spherical form of the central capsule and the enclosing shell, which here becomes ellipsoidal.
1. Belonaspis pandanus, n. sp.
Parmal pores elliptical, three or four times as large as the circular sutural pores. Each plate surrounded by five or six sutural pores (a single one on each side). Spines compressed, triangular; outer part half as long as the inner, and twice as long as the numerous, simple, bristle-shaped by-spines.
Dimensions.—Length of the ellipsoidal shell (or major axis) 0.12, breadth (or minor axis) 0.1; length of the spines 0.03, basal breadth 0.02.
Habitat.—South Pacific, Station 295, surface.
2. Belonaspis furcata, n. sp.
Parmal pores elliptical, twice as broad as the circular sutural pores. Each plate surrounded by five or six sutural pores (a single one on each side). Spines compressed, linear, very thin; outer part longer than the inner. By-spines very numerous, half as long as the radius, furcate, with divergent fork-branches.
Dimensions.—Length of the shell 0.1, breadth 0.08; length of the spines 0.12, breadth 0.003.
Habitat.—Indian Ocean (Cocos Islands), Rabbe, surface.
3. Belonaspis datura, n. sp. (Pl. 139, fig. 9).
Parmal pores elliptical, three or four times as large as the circular sutural pores. Each plate surrounded by ten or twelve sutural pores (two on each side). Spines triangular, two-edged, about as long as the radius of the shell; gradually tapering from its surface towards both ends. By-spines very short and numerous, simple.
Dimensions.—Length of the shell 0.13, breadth 0.11; length of the spines 0.08, basal breadth 0.025.
Habitat.—Central Pacific, Station 271, surface.
4. Belonaspis lanceolata, n. sp.
Parmal pores elliptical, six or eight times as large as the small circular sutural pores. Each plate surrounded by ten to twelve sutural pores (two on each side). Spines lanceolate, flat, in the distal part needle-shaped, about as long as the diameter of the shell. By-spines very numerous, zigzag, half as long as the shell-radius.
Dimensions.—Length of the shell 0.15 breadth 0.13; length of the spines 0.14, basal breadth 0.03; length of the by-spines 0.04.
Habitat.—North Pacific, Station 235, surface.
5. Belonaspis conifera, n. sp.
Parmal pores kidney-shaped, three or four times as large as the small circular pores. Each plate surrounded by ten to twelve sutural pores (two on each side). Spines very thick, half as long in the outer conical part as in the inner cylindrical part. By-spines very short, conical.
Dimensions.—Length of the shell 0.2, breadth 0.16; length of the spines 0.05, basal breadth 0.03.
Habitat.—Central Pacific, Station 267, surface.
6. Belonaspis multiforis, n. sp.
Parmal pores circular, of the same size as the circular sutural pores. Each plate surrounded by fifteen to eighteen sutural pores (three on each side). Spines compressed, about as long as the radius. By-spines very numerous, zigzag, half as long as the radius.
Dimensions.—Length of the shell 0.22, breadth 0.18; length of the spines 0.12, basal breadth 0.012; length of the by-spines 0.06.
Habitat.—Equatorial Atlantic, Station 347, surface.
Genus 373. Dictyaspis,[3] n. gen.
Definition.—Belonaspida with forty parmal pores (two on each plate), without by-spines, but with a network of prominent crests on the dimply surface.
The genus Dictyaspis repeats among the Belonaspida the characteristic structure of Ceriaspis (among the Dorataspida), by the development of prominent crests forming a network with dimples on the outer surface of the shields. Either all the dimples or only a part of them are pierced by a pore. The forty aspinal pores are united in pairs in twenty larger dimples. The shell is usually very thick-walled and non-transparent.
1. Dictyaspis solidissima, Haeckel.
Surface of the shell with seventy to eighty funnel-shaped dimples, each of which is perforated at the base by one or two small meshes; twenty larger dimples in the centre of the plates (each with two elliptical aspinal pores), and fifty to sixty smaller sutural dimples between them (each with a single circular pore). All pores of nearly the same size. No blind dimples. Outer conical part of the thick radial spines of the same length as the inner cylindrical part. Radius of the shell four times as large as the thickness of its wall.
Dimensions.—Length of the shell 0.12, breadth 0.1; length of the spines 0.06, basal breadth 0.012.
Habitat.—Mediterranean (Messina), surface.
2. Dictyaspis favosa, n. sp.
Surface of the shell with one hundred and seventy to one hundred and ninety deep funnel-shaped dimples, seventy to eighty of which are perforated, the others blind; among the former each of the fifty to sixty smaller contains a single sutural pore, each of the twenty larger a couple of aspinal pores. All pores of nearly the same size. Outer part of the compressed two-edged spines triangular, half as long as the inner part. Radius of the shell six times as large as the thickness of its wall. (Differs from Ceriaspis favosa, Pl. 138, fig. 6, mainly in the ellipsoidal form of the shell and the different size and form of the spines.)
Dimensions.—Length of the shell 0.16, breadth 0.13; length of the spines 0.04, basal breadth 0.025.
Habitat.—Central Pacific, Station 265, surface.
3. Dictyaspis compacta, n. sp.
Surface of the shell with one hundred and seventy to one hundred and ninety deep funnel-shaped dimples, seventy to eighty of which are perforated, the others blind; among the former each of fifty to sixty each contain a single sutural pore, twenty each a couple of aspinal pores. All dimples nearly of the same size, very deep. Outer part of the compressed sword-like spines somewhat longer than the inner part. Radius of the dark shell only twice as large as the thickness of its compact wall.
Dimensions.—Length of the shell 0.18, breadth 0.15; length of the spines 0.12, basal breadth 0.02.
Habitat.—Central Pacific, Station 274, surface.
Genus 374. Coleaspis,[4] Haeckel, 1881, Prodromus, p. 468.
Definition.—Belonaspida with forty parmal pores (two on each plate), with numerous by-spines and with a network of prominent crests on the dimpled surface.
The genus Coleaspis differs from its ancestral genus Dictyaspis in the development of numerous by-spines, and bears therefore among the ellipsoidal Belonaspida the same relation to it as Hystrichaspis does to Coscinaspis among the spherical Dorataspida. If the four equatorial spines in Coleaspis become different in pairs, it passes over into Hexalaspis. The shell is usually very dark and thick-walled.
1. Coleaspis coronata, n. sp.
All twenty spines of nearly equal size and form, about as long as the radius of the shell, compressed, sword-like, two-edged; both equatorial spines of the hydrotomical axis little longer than the eighteen others. Crests between the dimples of the shell-surface dentated, forming around the basal half of each spine a cylindrical sheath with a dentated, crown-like mouth, the teeth of which are prolonged into simple by-spines. (Similar to Hexaconus coronatus, Pl. 139, fig. 5, but differing in the nearly equal size of the spines and their sheaths, and in the longer by-spines.)
Dimensions.—Major axis of the shell 0.2, minor 0.17; length of the spines 0.12, basal breadth 0.02.
Habitat.—Central Pacific, Station 266, surface.
2. Coleaspis vaginata, n. sp. (Pl. 140, fig. 13).
All twenty spines of nearly equal size and form, nearly as long as the diameter of the shell, conical; both equatorial spines of the hydrotomical axis about one-third longer than the eighteen others. Crests between the dimples of the shell-surface serrated, forming around the basal half of each spine a conical truncate sheath with crested surface and serrated mouth, the teeth of which are prolonged into short by-spines. (Similar to Hexaconus vaginatus, Pl. 139, fig. 7, but differing in the nearly equal size of all the spines and in the double thickness of the shell-wall.)
Dimensions.—Major axis of the shell 0.12, minor 0.1, length of the spines 0.08, basal breadth 0.01.
Habitat.—North Pacific, Station 253, surface.
3. Coleaspis obscura, n. sp.
All twenty spines of nearly equal size and form, little longer than their large cylindrical sheaths, which are nearly as long as the radius of the shell, and armed on the truncated mouth with strong triangular by-spines, both equatorial spines of the hydrotomical axis one and a half times as long as the eighteen others. Shell very dark and thick walled, quite opaque.
Dimensions.—Major axis of the shell 0.1, minor 0.08; length of the spines 0.06, of their sheaths 0.04.
Habitat.—Arctic Ocean, Greenland, Koch, surface.
4. Coleaspis occulta, n. sp.
All twenty spines of nearly equal size and form, quite concealed in their long cylindrical sheaths, which are somewhat longer than the radius of the shell, and armed on the truncated mouth with acute simple teeth; each sheath deeply sulcated, apparently resulting from the concrescence of numerous parallel leaf-shaped by-spines. Small shell very dark and thick-walled, quite opaque.
Dimensions.—Major axis of the shell 0.08, minor 0.06; length of the spines and their sheaths 0.05 to 0.06.
Habitat.—Antarctic Ocean (off Kerguelen), Station 159, surface.
Subgenus 2. Coleaspidium, Haeckel.
Definition.—Both equatorial spines of the hydrotomical axis much larger and of peculiar form, different from the eighteen other spines.
5. Coleaspis amphilonche, n. sp.
Both equatorial spines of the hydrotomical axis much longer than the eighteen others, and of very different form; one and a half times as long as the diameter of the shell, prismatic, with six prominent edges, pyramidal at the distal point. The eighteen other spines triangular, compressed, two-edged, scarcely as long as the radius of the thick-walled shell. Pores of the shell irregular polygonal, separated by ciliated crests, which bear simple by-spines (one-third as long as the radius).
Dimensions.—Major axis of the shell 0.15, minor 0.12; length of the two larger spines 0.22, of the eighteen smaller 0.06 to 0.08; basal breadth of the former 0.03, of the latter 0.008.
Habitat.—South Atlantic, Station 341, surface.
6. Coleaspis hydrotomica, n. sp. (Pl. 140, fig. 14).
Both equatorial spines of the hydrotomical axis much larger than the eighteen others, and of very different form; about as long as the diameter of the shell, in the basal half four-sided pyramidal, with four thick prominent edges, in the middle part constricted, in the distal half lanceolate, two-edged. Both equatorial spines of the geotomical axis of similar form, but much smaller, scarcely one-third as long. The sixteen other spines sword-like, thin, two-edged, about as long as the radius of the thick-walled shell. Pores of the shell irregular roundish, separated by high dentated crests, which bears zigzag by-spines (half as long as the radius).
Dimensions.—Major axis of the shell 0.12, minor axis 0.1; length of the two larger spines 0.11, of the eighteen others 0.04 to 0.06; basal breadth of the former 0.04, of the latter 0.01.
Habitat.—Cape of Good Hope, Station 143, surface.
Genus 375. Phatnaspis,[5] Haeckel, 1881, Prodromus, p. 468
Definition.—Belonaspida with eighty to two thousand or more parmal pores (four to one hundred or more on each plate), without by-spines on the surface.
The genus Phatnaspis corresponds to the spherical Coscinaspis among the Dorataspida, and differs from the other Belonaspida in the great number of the parmal pores; whilst the four other preceding genera exhibit only two opposite aspinal pores in the centre of each plate, in this there are constantly numerous coronal pores in addition to these, and the plates always possess the characteristic form of a wainscotted or panelled work, with quadrangular meshes. The number of these parmal pores amounts in each plate to from ten to twenty, often one hundred and twenty or more; therefore the number of parmal pores in the whole shell amounts to two thousand or more. Sometimes the pores are circular, but in this case too they are surrounded by quadrangular frames. The quadrangles are sometimes quite regular squares, sometimes more or less irregular. The thin and fragile bars between the quadrangular pores form in each plate two peculiar systems of parallel crests, which cross at right angles. Commonly the parallel crests of one system (parallel to the major diameter of the compressed radial spines) are equidistant, and pierce from one edge of the plate to the opposite, whilst the parallel crests of the other system (parallel to the minor diameter of the spines) are interrupted and at different distances (Pl. 136, fig. 9); but in other species both crossed systems are quite regular. In each plate there is one primary diagonal rib (often stronger than the parallel crests) which connects the two opposite corners of the rhomboidal plate. We can distinguish in this genus three different subgenera: A. in Phatnasparium the primary diagonal rib arises from both flat sides of the compressed sword-like, radial spines; B. in Phatnasplenium from both sharp edges of them; C. in Phatnaspidium two crossed diagonal ribs arise from four edges of the spines (combination of A and B). Therefore in the first subgenus (A) two primary aspinal pores are placed opposite on the sharp edges of the spines, but in the second (B) inversely on their flat sides; in the third (C) there are apparently four primary aspinal pores, which are probably derived from B or A by division of the two pores.
Subgenus 1. Phatnasparium, Haeckel.
Definition.—In the centre of each rhomboidal plate two primary aspinal pores, opposite on both edges of the compressed spines, from both flat sides of which the primary diagonal crest arises.
1. Phatnaspis lacunaria, n. sp. (Pl. 136, fig. 9).
Parmal pores irregular quadrangular, of unequal size and form, ten to twelve on each side of the primary diagonal rib, which arises from both flat sides of the two-edged spines; two primary aspinal pores opposite on both edges of the latter. Spines much compressed, sword-like, their outer half shorter than the inner.
Dimensions.—Length of the shell 0.21 to 0.23, breadth 0.18 to 0.2; basal breadth of the spines 0.01.
Habitat.—Central Pacific, Station 268, surface.
2. Phatnaspis ensiformis, n. sp.
Parmal pores irregular quadrangular, of unequal size and form, six to eight on each side of the primary diagonal rib, which arises from both flat sides of the two-edged spines; two primary aspinal pores opposite on the two edges of the latter. Spines very broad, strongly compressed, sword-like, their outer half larger than the inner.
Dimensions.—Length of the shell 0.16, breadth 0.11; basal breadth of the spines 0.02.
Habitat.—Tropical Atlantic, Station 348, surface.
3. Phatnaspis loculata, n. sp.
Parmal pores regular quadrangular, of nearly equal size and form, twelve to sixteen on each side of the primary diagonal rib, which arises from both flat sides of the two-edged spines; two primary aspinal pores on the two edges of the latter. Spines linear, compressed, very long and thin, their outer half three to four times as long as the inner.
Dimensions.—Length of the shell 0.24, breadth 0.18; breadth of the spines 0.004.
Habitat.—North Atlantic, Station 354, surface.
4. Phatnaspis fenestrata, Haeckel.
Parmal pores regular quadrangular, of nearly equal size and form, six to eight on each side of the primary diagonal rib, which arises from both flat sides of the two-edged spines; two primary aspinal pores on the two edges of the latter. Spines linear, little compressed, or nearly needle-shaped, very long and thin, their outer half five to ten times as long as the inner.
Dimensions.—Length of the shell 0.11 to 0.12, breadth 0.07 to 0.08; breadth of the spines 0.002.
Habitat.—Mediterranean (Messina), surface.
5. Phatnaspis cristata, n. sp. (Pl. 136, fig. 6).
Parmal pores circular, of very different size, separated by high square crests, ten to twelve on each side of the high, comb-like, primary diagonal rib, which arises from both flat sides of the two-edged spines; two primary aspinal pores on the two edges of the latter. Each circular pore is surrounded by a square frame. Spines sword-like, strongly compressed, their outer part longer than the inner.
Dimensions.—Length of the shell 0.2 to 0.22, breadth 0.16 to 0.18; basal breadth of the spines 0.01.
Habitat.—North Pacific, Station 254, surface.
6. Phatnaspis coscinoides, n. sp.
Parmal pores circular, regular, all of nearly equal size, twelve to sixteen on each side of the primary diagonal rib, which arises from both flat sides of the two-edged spines; two primary pores on the two edges of the latter. Spines linear, little compressed, their outer part much longer than the inner.
Dimensions.—Length of the shell 0.18, breadth 0.15; breadth of the spines 0.006.
Habitat.—South Atlantic, Station 325, surface.
Subgenus 2. Phatnasplenium, Haeckel.
Definition.—In the centre of each rhomboidal plate two primary aspinal pores, opposite on the two flat sides of the compressed spines, from the two edges of which the primary diagonal crest arises.
7. Phatnaspis orthopora, n. sp.
Parmal pores irregular quadrangular, of unequal size and form, four to six on each side of the primary diagonal rib, which arises from both edges of the compressed spines; two larger primary aspinal pores opposite on the two flat sides of the latter. Spines very thin and long, linear, their outer half three to four times as long as the inner.
Dimensions.—Length of the shell 0.08, breadth 0.06; breadth of the spines 0.003.
Habitat.—North Atlantic, Station 353, surface.
8. Phatnaspis polypora, n. sp.
Parmal pores irregular polygonal, of very unequal size and form, sixteen to twenty on each side of the primary diagonal rib, which arises from both edges of the compressed spines; two very large, lanceolate, primary aspinal pores opposite on the two flat sides of the latter. Spines very thin, linear, on the outside of the shell rudimentary. (This remarkable species somewhat resembles Coscinaspis polypora, Pl. 136, fig. 8.)
Dimensions.—Length of the shell 0.32, breadth 0.24; breadth of the spines 0.002.
Habitat.—South Atlantic, Station 332, surface.
9. Phatnaspis quadratura, n. sp.
Parmal pores regular, square, all of nearly equal size and form, ten to twelve on each side of the primary diagonal rib, which arises from both edges of the compressed spines; two primary aspinal pores opposite on the two flat sides of the latter, not different from the other pores. Spines sword-like, their outer part about as long as the inner.
Dimensions.—Length of the shell 0.2, breadth 0.16; basal breadth of the spines 0.004.
Habitat.—Central Pacific, Station 274, surface.
10. Phatnaspis tabulata, Haeckel.
Parmal pores regular, circular, with square frames, all of nearly equal size, eight to ten on each side of the primary diagonal rib, which arises from both edges of the compressed spines; two primary aspinal pores opposite on the flat sides of the latter. Spines sword-like, short, scarcely half as long as the radius of the shell, their central ends are thickened and cause by their union the deceptive appearance of an enclosed "medullary shell."
Dimensions.—Length of the shell 0.12 to 0.15, breadth 0.1 to 0.12; breadth of the spines 0.006.
Habitat.—Mediterranean; Nice, Müller; Portofino, near Genoa, Haeckel, surface.
Subgenus 3. Phatnaspidium, Haeckel.
Definition.—In the centre of each rhomboidal plate four primary aspinal spines, forming a regular cross, the centre of which receives the cylindrical or four-sided prismatic spine.
11. Phatnaspis haliommidium, n. sp. (Pl. 136, fig. 7).
Parmal pores irregular quadrangular, of unequal size and form, eight to ten on each side of the crossed diagonal ribs, which arise at right angles from the four edges of the prismatic spines; four primary aspinal pores not different from the others. Outer part of the strong spines scarcely longer than the inner. (Resembling Icosaspis tabulata, Pl. 136, fig. 2, which, however, is distinguished by the spherical shell and the larger pores.)
Dimensions.—Length of the shell 0.22, breadth 0.17; breadth of the spines 0.016.
Habitat.—North Pacific, Station 244, surface.
12. Phatnaspis mülleri, n. sp.
Parmal pores regular, square, all of nearly equal size and form, twelve to sixteen on each side of the crossed diagonal ribs, which arise at right angles from the needle-shaped spines; the four primary aspinal pores not different from the others. Spines very thin and long, cylindrical; four to six times longer in the outer than in the inner part.
Dimensions.—Length of the shell 0.24, breadth 0.16; breadth of the spines 0.002.
Habitat.—Mediterranean (Messina), surface.
Family XLIII. Hexalaspida, n. fam. (Pl. 139).
Definition.—Acantharia with a simple discoidal or lenticular lattice-shell, composed of the branched apophyses of twenty radial spines meeting in the centre and disposed according to the Müllerian law of Icosacantha. Six larger spines in the hydrotomical plane, prominent on the margin of the circular or elliptical biconvex lens. Fourteen other spines much smaller or rudimentary. Central capsule biconvex lenticular, enclosed in the fenestrated shell.
The family Hexalaspida represents a new small, but very interesting group of Acanthophracta, which differs from all others in the lentelliptical or triaxial form of the lenticular lattice-shell, the margin of which bears six larger spines placed in the hydrotomical plane (compare above, p. 719). They may therefore be characterised shortly as "Acanthophracta lentelliptica," with three different dimensive axes and six larger marginal spines. A closer comparison with the other Acantharia leaves no doubt that the Hexalaspida must be derived from the Belonaspida by stronger development of six radial spines placed in the hydrotomical plane, namely, two equatorial and four associated polar spines; whilst the six spines of the geotomical plane (perpendicular to the former) are much smaller; the eight tropical spines are intermediate in size between the former and the latter.
The geometrical fundamental form of the Hexalaspida (of the central capsule as well as of the enclosing shell) is therefore lentelliptical, with three different dimensive axes, and they exhibit among the Acantharia a relation to the spherical Dorataspida and the ellipsoidal Belonaspida similar to that which the lentelliptical Larcoidea exhibit to the spherical Sphæroidea and the ellipsoidal Prunoidea among the Sphærellaria (compare above, p. 599). The largest of the three dimensive axes (which are perpendicular to one another) is here the hydrotomical axis, the shortest, on the contrary, the geotomical axis; the intermediate in size being the spineless axis. The development of the whole body is strongest in the hydrotomical meridian plane, in which the six principal spines are placed; it is weakest in the geotomical plane, in which the six smallest spines are placed; the eight tropical spines are intermediate in size between the others. This peculiar development is illustrated by the figures of Pl. 139, where the four equatorial spines are everywhere marked by c, the eight tropical spines by b and d, the eight polar spines by a and e.
Rarely the six hydrotomical or principal spines are of equal size, and thus the margin of the shell may be quite circular or regularly hexagonal (Pl. 139, figs. 1-3); the two equatorial spines of the hydrotomical plane are usually larger than its four polar spines, and thus the margin of the shell becomes more or less elliptical (Pl. 139, figs. 4-7). Usually (almost constantly) these six larger spines are more or less compressed, triangular, often very broad and flat; their two edges lie in the hydrotomical plane. Their two flat surfaces are often furrowed, with longitudinal ribs or crests converging towards the simple apex of the spines.
The fourteen smaller spines are regularly disposed according to the Müllerian law of Icosacantha on both convex sides of the lenticular shell; they are not only smaller than the six principal spines, but often also of different form, much thinner and shorter, sometimes needle-shaped. In the genera Hexonaspis and Hexacolpus (Pl. 139, figs. 1, 2) only their inner part (inside of the shell) is developed, whilst their outer part is quite rudimentary and not prominent on the surface. Therefore these genera appear to possess only six marginal spines externally.
The Lenticular Shell itself offers in the Hexalaspida great difficulties in the way of accurate study, as its wall is constantly very thick and dark, often quite opaque and non-transparent. However, prolonged accurate researches have convinced me that its structure is essentially the same as in the Belonaspida and especially in the genera Dictyaspis and Coleaspis. As in these latter the twenty plates of the shell bear high crests or combs on the outer surface, and by these funnel-shaped dimples are separated. The network of these crests is more or less regular (Pl. 139, figs. 1-7). Around the base of each radial spine the shell is usually elevated in the form of a conical or cylindrical sheath; the crests are prolonged into the sheaths as longitudinal ribs, parallel to the spine or convergent towards its apex. Whilst in Hexalaspis and Hexonaspis these basal sheaths are not at all or but little prominent (Pl. 139, fig. 2; Pl. 140, fig. 16), in Hexaconus and Hexacolpus they envelop the basal half (or even more) of the spines, and very often the circular or elliptical free distal edge of the sheath is elegantly denticulated or serrated (Pl. 139, figs. 1, 3-7; pl. 140, figs. 9-16).
The Pores of the shell exhibit in the Hexalaspida the same shape as in the majority of the Belonaspida. Each spine bears only two broad opposite apophyses, the fork-branches of which unite to form a polygonal shield with two pores. The number of parmal pores is constantly (?) forty, as each plate possesses only two primary aspinal pores; there are no secondary or coronal pores. The numerous (between fifty and one hundred, rarely more) smaller pores between the forty parmal pores are probably always sutural pores; however, their number and position is very difficult to determine, on account of the high protecting crests; the majority of the funnel-shaped dimples between the latter seem to be blind, not perforated. Sometimes all the dimples, except the twenty spinal ones, seem to be blind and the sutural pores appear to have disappeared completely, so that there remain only twenty aspinal pores (Pl. 139, fig. 4).
The internal cavity of the shell in all Hexalaspida is very small, on account of the thickness of the massive wall; the latter is often greater than the diameter of the cavity. Setting aside this disproportion, the space of the cavity is further much reduced by the internal parts of the thick radial spines, which are united in the centre by their pyramidal bases (Pl. 140, fig. 15). Usually the twenty bases seem to remain free (supported one upon another by means of their triangular faces); but sometimes they seem to grow together perfectly and to form a single central star of acanthin. In some species, too, the sutures of the meeting branches of the apophyses of neighbouring spines seem to grow together, so that the whole shell exhibits a single piece of acanthin.
The Central Capsule of the Hexalaspida is therefore very small and seems to fill up the greatest part of the shell-cavity. Its form is constantly more or less lenticular, sometimes lentelliptical. On account of the opacity of the shell I could not make out its shape more closely.
Synopsis of the Genera of Hexalaspida.
| All twenty spines externally developed, prominent on the surface of the lenticular shell. | Sheaths of the spines not prominent, | 376. Hexalaspis. | |
| Sheaths of the spines prominent, | 377. Hexaconus. | ||
| Only six spines (the hydrotomical spines) externally developed and prominent on the margin of the disk; the other fourteen spines not prominent. | Sheaths of the spines not prominent, | 378. Hexonaspis. | |
| Sheaths of the spines prominent, | 379. Hexacolpus. |
Genus 376. Hexalaspis,[6] n. gen.
Definition.—Hexalaspida with twenty prominent radial spines, which are not surrounded by prominent sheaths; the six hydrotomical spines much larger than the fourteen others.
The genus Hexalaspis is the simplest form among the Hexalaspida, and may be derived directly from Dictyaspis among the Belonaspida, by stronger development of the six hydrotomical spines. As in the following genus Hexaconus all twenty spines are prominent externally.
Subgenus 1. Hexalasparium, Haeckel.
Definition.—Six hydrotomical spines of equal size.
1. Hexalaspis heliodiscus, n. sp. (Pl. 139, fig. 2).
All six hydrotomical spines of nearly equal size (or sometimes the two equatorial a little larger than the four polar spines), isosceles triangular, compressed, smooth; about as long as the radius of the shell, and half as broad at the base. The fourteen other spines very small, also triangular and compressed, but little prominent on the two convex sides of the lenticular shell.
Dimensions.—Diameter of the shell 0.11; length of the six hydrotomical spines 0.05, basal breadth 0.03.
Habitat.—Central Pacific, Station 271 to 274, surface.
2. Hexalaspis stellata, n. sp.
All six hydrotomical spines of nearly equal size, lanceolate compressed, with two longitudinal furrows on each flat side, about as long as the diameter of the shell, and one-fourth as broad at the base. The fourteen other spines very thin, also compressed, half as long and only one-fourth as broad as the six large spines.
Dimensions.—Diameter of the shell 0.14; length of the six hydrotomical spines 0.13, basal breadth 0.035.
Habitat.—South Pacific, Station 284, surface.
Subgenus 2. Hexalaspidium, Haeckel.
Definition.—Six hydrotomical spines of unequal size, two opposite (equatorial) much larger than the four other (polar) spines.
3. Hexalaspis sexalata, n. sp.
Six hydrotomical spines of unequal size; the two equatorial spines about as long as the shell-radius and twice as long as the four polar spines, which are isosceles triangular. The fourteen other spines are only half as long and one-fourth as broad as the latter, little prominent. (Resembles Hexonaspis hastata, Pl. 140, fig. 16, which is distinguishable by the furrows on the six spines and by the total absence of the fourteen external rudimentary spines.)
Dimensions.—Diameter of the shell 0.15; length of the two equatorial spines 0.08, of the four polar spines 0.04, of the fourteen other spines 0.02.
Habitat.—North Pacific, Station 240, surface.
4. Hexalaspis hexalastrum, n. sp.
Six hydrotomical spines of unequal size; the two equatorial spines somewhat longer than the diameter of the shell and three times as long as the four polar spines, all six triangular, smooth, of the same basal breadth (equal to half the radius). The fourteen other spines very thin, conical at the base, nearly as long as the radius.
Dimensions.—Diameter of the shell 0.21; length of the two equatorial spines 0.24, of the eighteen others 0.08 to 0.1; basal breadth of the six larger spines 0.05, of the fourteen others 0.01.
Habitat.—Western Tropical Pacific, Station 224, surface.
5. Hexalaspis hexaglypha, n. sp.
Six hydrotomical spines of unequal size; the two equatorial very large, six-sided prismatic, twice as long as the diameter of the shell and four times as long as the four pyramidal polar spines; each of these six spines with six deep furrows between the six prominent edges. The fourteen other spines very thin, compressed, two-edged, about as long as the radius of the shell.
Dimensions.—Diameter of the shell 0.11; length of the two equatorial spines 0.2, of the eighteen others 0.04 to 0.06; basal breadth of the six larger spines 0.03, of the fourteen others 0.01.
Habitat.—Tropical Atlantic, Station 352, surface.
Genus 377. Hexaconus,[7] n. gen.
Definition.—Hexalaspida with twenty prominent radial spines, which are surrounded at the base by prominent sheaths; the six hydrotomical spines much larger than the fourteen others.
The genus Hexaconus differs from the preceding Hexalaspis in the development of conical or cylindrical sheaths surrounding the basal parts of the radial spines; these sheaths are developed sometimes around all twenty spines, sometimes only around the six larger hydrotomical spines.
Subgenus 1. Hexaconarium, Haeckel.
Definition.—Six hydrotomical spines of equal size.
1. Hexaconus ciliatus, n. sp. (Pl. 139, fig. 3).
All six hydrotomical spines of nearly equal size, pyramidal, with six prominent edges, somewhat longer than the radius of the shell. Sheaths sulcated, finely ciliated at the mouth, twice as broad as long and only one-fourth as long as the spines. The fourteen smaller spines very thin, bristle-shaped, shorter than the radius of the shell.
Dimensions.—Diameter of the shell 0.16; length of the six hydrotomical spines 0.11; basal breadth 0.03.
Habitat.—Central Pacific, Station 270, surface.
2. Hexaconus coronatus, n. sp. (Pl. 139, fig. 5).
All six hydrotomical spines of equal size, conical, somewhat compressed, with two prominent edges, scarcely as long as the radius of the shell. Sheaths crested, strongly dentated on the mouth, three times as broad as long and only one-sixth as long as the spines. Fourteen smaller spines about half as large as the six principal spines, of the same form, but without coronated sheaths.
Dimensions.—Diameter of the shell 0.2; length of the six hydrotomical spines 0.1; basal breadth 0.02.
Habitat.—North Pacific, Station 253, surface.
3. Hexaconus velatus, n. sp. (Pl. 139, fig. 6).
All six hydrotomical spines of equal size, conical, somewhat compressed, shorter than the radius of the shell. Sheaths very large, truncated conical, enveloping the spines almost entirely, with crested wall, only half as broad at the constricted mouth as at the base. The fourteen smaller spines about half as large as the six principal spines, of the same form, but without large sheaths.
Dimensions.—Diameter of the shell 0.12; length of the six hydrotomical spines 0.05; basal breadth 0.01.
Habitat.—North Atlantic, Station 354, surface.
Subgenus 2. Hexaconidium, Haeckel.
Definition.—Six hydrotomical spines of unequal size, two opposite (equatorial) much larger than the four other (polar) spines.
4. Hexaconus serratus, n. sp. (Pl. 139, fig. 4).
Six hydrotomical spines of unequal size, the two equatorial being as long as the radius of the shell and one and a half times as large as the four polar; all of the same form, triangular, compressed, with six prominent edges. Sheaths cylindrical, half as long as the spines, with prominent crests, and with strong serrated teeth at the distal mouth. The fourteen smaller spines scarcely one-fourth or one-sixth as large as the six principal spines, without prominent sheaths.
Dimensions.—Diameter of the shell 0.2; length of the equatorial spines 0.1, basal breadth 0.05; length and breadth of the sheaths 0.05.
Habitat.—South Pacific, Station 288, surface.
5. Hexaconus vaginatus, n. sp. (Pl. 139, fig. 7).
Six hydrotomical spines of unequal size; the two equatorial very stout, pyramidal, six-edged, nearly as long as the diameter of the shell, and on the base three to four times as broad as the eighteen other spines, which are much thinner, all nearly of equal length, and two-edged. All twenty spines are provided with prominent basal sheaths, which are truncate conical, sulcate, and dentate on the narrowed distal mouth. The sheaths of the six hydrotomical spines are twice to three times as large as those of the fourteen smaller spines.
Dimensions.—Diameter of the shell 0.15; length of the spines 0.12; basal breadth of the equatorial spines 0.04, of the other spines 0.02; length of the hydrotomical sheaths 0.05, of the other sheaths 0.02.
Habitat.—Central Pacific, Station 274, surface.
6. Hexaconus echinatus, n. sp. (Pl. 140, fig. 12).
Six hydrotomical spines of unequal size; the two equatorial, and their sheaths twice as large as the four polar spines. These six spines are six-edged, pyramidal, and their basal half enveloped by very large conical sheaths which are sulcate, and twice as broad on the dentate distal mouth as on the narrower base. The other fourteen spines are very thin, two-edged, half as long, with low sheaths. Approaches some forms of Diploconus.
Dimensions.—Diameter of the shell 0.15; length of the equatorial spines 0.13, of the polar spines 0.08.
Habitat.—Indian Ocean, Belligemma, Ceylon, Haeckel, surface.
Genus 378. Hexonaspis,[8] n. gen.
Definition.—Hexalaspida with six prominent radial spines (in the hydrotomical plane) which are not surrounded by prominent sheaths; the fourteen other spines quite rudimentary, not prominent.
The genus Hexonaspis and the following Hexacolpus differ from the two preceding genera in the rudimentary shape of the fourteen reduced and stunted smaller spines; these are only developed inside the shell, and are not prominent outside over its surface.
Subgenus 1. Hexonasparium, Haeckel.
Definition.—Six hydrotomical spines of equal size.
1. Hexonaspis heliosestrum, n. sp.
All six hydrotomical spines of nearly equal size, isosceles triangular, compressed, smooth, about as long as the diameter of the shell and three times as long as broad at the base. This species is very similar to Hexalaspis heliodiscus (Pl. 139, fig. 2), but differs in the larger size of the six marginal spines and in the complete external absence of the fourteen smaller spines.
Dimensions.—Diameter of the shell 0.13; length of the six marginal spines 0.12, basal breadth 0.04.
Habitat.—Tropical Atlantic, Station 348, surface.
2. Hexonaspis hexapleura, n. sp. (Pl. 140, fig. 15).
All six hydrotomical spines of nearly equal size, triangular, compressed, six-edged, about as long as the radius of the shell and twice as long as broad on the base. Two strong prominent ribs on each flat side of the spines. Shell very thick-walled, with a very small cavity.
Dimensions.—Diameter of the shell 0.11; length of the six marginal spines 0.06, basal breadth 0.03.
Habitat.—South Atlantic, Station 332, surface.
3. Hexonaspis hexagona, n. sp.
All six hydrotomical spines of equal size, very short, triangular, only half as long as broad at the base. The whole shell accordingly forms a regular hexagon, the six corners of which are formed by the distal points of the rudimentary spines, the six sides by their straight lateral edges. Shell very dark.
Dimensions.—Diameter of the shell 0.2; length of the six marginal spines 0.03, basal breadth 0.06.
Habitat.—South Atlantic (east of Patagonia), Station 318, surface.
Subgenus 2. Hexonaspidium, Haeckel.
Definition.—Six hydrotomical spines of unequal size, two opposite (equatorial) much larger than the four other (polar) spines.
4. Hexonaspis hastata, n. sp. (Pl. 140, fig. 16).
Six hydrotomical spines of unequal size; two larger equatorial spines with six prominent wings, about as long as the radius of the shell and half as broad at the base; the four polar spines quite as broad, but only half as long, nearly equilateral triangular, with two shallow furrows on each flat side at the broader base. The fourteen smaller spines not visible on the surface, quite rudimentary. Crests of the surface elegantly denticulated.
Dimensions.—Diameter of the shell 0.14; length of the two equatorial spines 0.08, of the four polar spines 0.04; basal breadth 0.04.
Habitat.—Central Pacific, Station 271, surface.
Genus 379. Hexacolpus,[9] n. gen.
Definition.—Hexalaspida with six prominent radial spines (in the hydrotomical plane), which are surrounded by prominent sheaths at the base; the fourteen other spines quite rudimentary, not prominent.
The genus Hexacolpus differs from the preceding Hexonaspis in the development of conical or cylindrical sheaths around the basal parts of the radial spines. It bears to the latter the same relation as Hexaconus exhibits to Hexalaspis.
Subgenus 1. Hexacolparium, Haeckel.
Definition.—Six hydrotomical spines all nearly of equal size.
1. Hexacolpus nivalis, n. sp. (Pl. 139, fig. 1).
All six hydrotomical spines of nearly equal size and equidistant, thin, lanceolate, compressed, somewhat shorter than the diameter of the hexagonal shell. Sheaths nearly prismatic, conical in the distal third, each with twelve prominent parallel crests, which are separated by twelve deep furrows; their contracted distal opening or mouth denticulate. The sheaths are as long as the radius of the shell, and envelop two-thirds of the spines. (Resembles certain forms of snow-crystals.)
Dimensions.—Diameter of the shell 0.15, thickness of its wall 0.08; length of the spines 0.1, of the sheath 0.007; breadth of the latter 0.04.
Habitat.—West Tropical Pacific, Station 225, surface.
2. Hexacolpus conifer, n. sp.
All six hydrotomical spines of equal size and equidistant, triangular, compressed, about as long as the radius of the circular shell. Sheaths conical, sulcate, half as broad on the serrate distal end as on the base. The sheaths envelop the basal half of the spines.
Dimensions.—Diameter of the shell 0.18; length of the spines 0.1, of the sheaths 0.06; basal breadth of the latter 0.07, distal breadth 0.04.
Habitat.—North Pacific, Station 236, surface.
Subgenus 2. Hexacolpidium, Haeckel.
Definition.—Six hydrotomical spines of unequal size, two opposite (equatorial) much larger than the four other (polar) spines.
3. Hexacolpus trypanon, n. sp. (Pl. 140, fig. 11).
Six hydrotomical spines of unequal size, two equatorial about as long as the diameter of the shell and nearly twice as large as the four polar; all of the same form, quadrangular prismatic, with prominent edges and pointed distal ends. Sheaths six-sided prismatic, with strong prominent edges and thinner parallel ribs between them; their distal mouth with six strong denticulated teeth. The sheaths envelop two-thirds of the spines, and are as broad as the radius of the shell.
Dimensions.—Diameter of the shell 0.13; length of the equatorial spines 0.12, of their sheaths 0.08; breadth of the latter 0.06.
Habitat.—South Pacific, Station 288, surface.
4. Hexacolpus dodecodus, n. sp.
Six hydrotomical spines of unequal size, two equatorial about as long as the radius of the shell and twice as large as the four polar; all of the same form, triangular, compressed, sulcated. Sheaths prismatic, with twelve prominent, parallel edges, and twelve strong serrated triangular teeth on the mouth. The sheaths envelop the basal half of the spines. This species greatly resembles Hexaconus serratus (Pl. 139, fig. 4), but differs in the larger size of the equatorial spines and the complete reduction of the fourteen smaller spines.
Dimensions.—Diameter of the shell 0.2; length of the equatorial spines 0.1, of their sheaths 0.06; breadth of the latter 0.08.
Habitat.—North Pacific, Station 248, surface.
5. Hexacolpus infundibulum, n. sp. (Pl. 140, fig. 10).
Six hydrotomical spines of unequal size, two equatorial about twice as long as the diameter of the shell and as the four polar spines; all six spines of the same form, quadrangular prismatic, pointed at the distal pyramidal end. Sheaths conical, two to three times as broad at the denticulate distal mouth as at the narrow base, sulcate; the mantle of the cone concavely vaulted. The large sheaths envelop two-thirds or three-fourths of the spines.
Dimensions.—Diameter of the shell 0.1 to 0.13; length of the equatorial spines 0.15 to 0.2, of their sheaths 0.1 to 0.15; basal breadth of the latter 0.04, distal breadth 0.12.
Habitat.—Central Pacific, Station 272, surface.
Family XLIV. Diploconida, Haeckel (Pl. 140).
Diploconida, Haeckel, 1862, Monogr. d. Radiol., p.404.
Definition.—Acantharia with simple diploconical shell, composed of two very large equatorial spines which are opposite in the hydrotomical axis, are surrounded by conical or cylindrical, often compressed sheaths, and arise from a small central lattice-shell. Eighteen other spines (disposed according to the Müllerian law of Icosacantha) much smaller, often rudimentary. Central capsule ellipsoidal or diploconical.
The family Diploconida, founded by me in 1862 for a single Mediterranean species (Diploconus fasces), appears to be the most aberrant and strange form among the Acantharia. As I had met with only a single specimen, very dark and intransparent in its central part, my observations on its structure were imperfect and the explanation of it partly erroneous (compare my Monograph, pp. 46, 404, Taf. xx. figs. 7, 8). However, I regarded Diploconus as the representative of quite a peculiar family, derived from the Acanthometrida, and I correctly compared the large opposite radial spines of one equatorial axis with the corresponding parts in Amphilonche.
Afterwards Richard Hertwig observed some specimens of Diploconus fasces in the same locality (Messina), and gave an accurate description of its central capsule, including numerous small nuclei (1879, Organismus d. Radiol., p. 28, Taf. ii. fig. 3). He found also that the peculiar diploconical skeleton is not composed of silex, but of acanthin. In the explanation of the shell-structure he adopted my opinion.
In the rich collections of the Challenger I detected ten different forms of Diploconida, all very rare, and for the most part represented only by single specimens. A twelfth species was found by me in the collection of Captain Rabbe from the Indian Ocean. By the study of these new forms, and particularly by their comparison with the most nearly allied Hexalaspida and Belonaspida, it was possible for me to correct some errors in my former description and to give a much more correct description and natural explanation of this very peculiar and strange family of Radiolaria (compare Pl. 140).
The most characteristic and the most voluminous part of the acanthinic skeleton in all Diploconida appears as the diploconical or nearly cylindrical solid "mantle" giving them their name and odd appearance (Pl. 140). Usually this mantle is broader on its two opposite terminal openings than in its more or less constricted middle part. This latter is now more spherical or ellipsoidal, now more lenticular, and usually separated from the two cones by two slight transverse strictures. On the surface of this middle part twelve to eighteen radial spines, which in Diplocolpus are rudimentary or absent, are visible in Diploconus. The longitudinal axis of this shell is constantly occupied by a very large pair of opposite stout prismatic or cylindrical principal spines, which are united in the centre and usually more or less prominent with their distal apex over the two openings of the double cone.
In my first communication on the Diploconus (1862, loc. cit.) I correctly compared these two large spines in the prolonged main axis of the shell to the principal equatorial spines of Amphilonche (or to the "hydrotomical spines," c1, c3); but my explanation of the two peculiar cones enveloping them was erroneous. I supposed at that time that they were formed by the eight flattened and leaf-shaped curved tropical spines, so that around each principal spine the four neighbouring tropical spines (two of the northern and two of the southern hemisphere) had grow together by their edges and formed the peculiar conical sheath. I can now say that this opinion (afterwards adopted also by Hertwig) was quite erroneous, the two conical or funnel-shaped sheaths being the enlarged basal sheaths of the two hydrotomical spines, which we have already seen in the Hexalaspida (Pl. 139). But whilst in these latter all six principal spines of the hydrotomical meridian plane are hypertrophied (two equatorial and four polar spines), in the nearly allied Diploconida only the two opposite equatorial spines are developed, whilst all other eighteen spines are more or less atrophied or quite rudimentary. In Diploconus the latter are more or less evident, whilst in Diplocolpus they disappear externally.
The true lattice-shell of the Acanthophracta (constantly composed of the meeting apophyses of twenty radial spines) is therefore represented in the Diploconida by the small roundish middle part of the whole shell, which is usually much smaller than the two opposite cones, and separated from them by the two slight transverse strictures. Usually this small but most important middle part of the shell is very dark and opaque, on account of its very thick wall and small pores; but in some species it is clear enough to ascertain that the structure of this lattice-shell is the same as in the lenticular Hexalaspida, there being a network of thick crests on the outer surface and small pores in the dimples between them. Indeed, in many (and probably in all) Diploconida the forty aspinal pores are present which we found in all Hexalaspida, Belonaspida, and Diporaspida, so that these four families of Acanthophracta represent one continuous phylogenetical series; Phractaspis among the Diporaspida is at the beginning, and Diplocolpus among the Diploconida at the end of this remarkably transformed morphological series.
The twenty radial spines in all Diploconida are probably united very firmly (or even perfectly grown together) in the centre of the small thick-walled lattice-shell, the inner space of which is extremely reduced. Probably, too, the sutures between the meeting apophyses of the thick radial spines are often (or even constantly) obliterated by concrescence, so that the whole shell forms a single piece of acanthin. But I regret that I cannot ascertain these and other points in the structure of the shell, as the small number of specimens observed did not permit an anatomical examination to be made. I have no doubt, however, that the structure of the whole of the middle main part of the shell is quite the same as in the lenticular shell of the thick-walled Hexalaspida, and that in both families each of the twenty radial spines bears originally only two opposite apophyses.
The characteristic mantle of the double cone of the Diploconida, or the basal sheath of their two large, perfectly developed principal spines is usually much larger than the shell itself, and more or less compressed from both poles of the shortened geotomical axis. Therefore the transverse section of the two cones is usually elliptical, more rarely circular. Their widest part is generally the distal opening; more rarely this is a little constricted. The thin transparent lamella of acanthin, representing the mantle of the double cone, is commonly ribbed or furrowed by longitudinal, parallel or divergent crests, and elegantly denticulated on the edge of the distal opening.
The two conical or cylindrical halves of the mantle are connected with the two enclosed principal spines not only at the base, where they arise from the small central lattice-shell, but also throughout a certain part of their length, by means of two, four, or six wings or leaves, which lie opposite and in pairs in the meridian planes of those spines. These meridian wings are more or less triangular (with broader concave outer bases), and connected by their axial edge with the spine and by their peripheral edge with the mantle. They separate two, four, or six conical spaces or pyramidal compartments in each cone. But these aspinal compartments and the separating septa are not new productions of the Diploconida, but are inherited from their ancestral family, the Hexalaspida (compare above, p. 873).
The eighteen smaller spines in Diploconus are either of nearly equal size or more or less differentiated. The eight tropical spines are often much larger than the eight polar spines. The two geotomical spines, (or the two opposite equatorial spines of the shortened geotomical axis) are often quite rudimentary. In Diplocolpus the external part (outside the shell) is in all eighteen smaller spines rudimentary or atrophied.
The Central Capsule, as shown by Hertwig, contains numerous small nuclei, and is divided into three parts by the above named two transverse strictures; the smaller central part (in the original lenticular lattice-shell) and the two opposite larger parts, filling up the greater part of the two conical or cylindrical sheaths, and more or less adopting their form. Corresponding to the shell itself the enclosed capsule is often more or less flattened, being compressed at both poles of the geotomical axis. The pseudopodia seem to proceed only from the two large polar apertures of the sheaths, and form therefore two opposite conical tufts or bunches.
Synopsis of the Genera of Diploconida.
| All twenty spines more or less developed (sometimes eight of them rudimentary), | 380. Diploconus. |
| Only the two hydrotomical spines developed (all the eighteen others rudimentary), | 381. Diplocolpus. |
Genus 380. Diploconus,[10] Haeckel, 1862, Monogr. d. Radiol., p. 404.
Definition.—Diploconida with two very large spines (opposite in the hydrotomical axis) and ten to eighteen other much smaller spines externally visible.
The genus Diploconus must be derived from Hexacolpus (among the Hexalaspida) by the stronger development of the two hydrotomical spines and their large sheaths; all the other eighteen spines are much smaller, and usually devoid of prominent sheaths. Sometimes the eight tropical spines are rudimentary.
Subgenus 1. Diploconulus, Haeckel.
Definition.—Mantle of the double cone not compressed; its transverse section therefore circular.
1. Diploconus amalla, n. sp. (Pl. 140, fig. 1).
Mantle of the double cone thick walled, not compressed, its transverse section circular; its contour little convex; its surface nearly smooth; its distal margin regularly denticulated. Diameter of its mouth twice as large as the equatorial diameter of the shell and one-third as long as its total length. The two large spines prismatic, one-fourth longer than their conical sheath. The eighteen smaller spines very thin, about half as long as the former, a little curved.
Dimensions.—Length of the shell 0.3; equatorial breadth 0.05, polar breadth 0.1.
Habitat.—Central Pacific, station 271, surface.
2. Diploconus cyathiscus, n. sp. (Pl. 140, fig. 3).
Mantle of the double cone thin walled, not compressed; its transverse section circular; its contour strongly convex; its surface with six stronger and many smaller ribs; its margin with numerous straight and long, parallel denticles. Diameter of its mouth half as long as the whole shell and one and a half times as long as its equatorial diameter. The two principal spines one-fourth longer than their conical sheath. The eighteen smaller spines about half as long, thin, straight. Both geotomical spines thick and short.
Dimensions.—Length of the shell 0.2; equatorial breadth 0.07, polar breadth 0.1.
Habitat.—West Tropical Pacific, Station 225, surface.
3. Diploconus cylindrus, n. sp.
Mantle of the double cone thick walled, dark, cylindrical, not compressed; its transverse section circular; its contours straight, parallel; its surface with strong parallel straight longitudinal ribs; its margin irregularly dentated. Diameter of its mouth one-fifth as long as the whole shell and two-thirds as long as the diameter of the equatorial intumescence. The two principal spines prismatic, nearly twice as long as their cylindrical sheath. The smaller spines about half as long, thin, conical, straight. (Resembles the medial part of Hexacolpus trypanon, Pl. 140, fig. 11.)
Dimensions.—Length of the shell 0.25; equatorial breadth 0.08, polar breadth 0.05.
Habitat.—North Pacific, Station 241, surface.
Subgenus 2. Diploconium, Haeckel.
Definition.—Mantle of the double cone compressed from both poles of the shortened geotomical axis; its transverse section therefore elliptical.
4. Diploconus fasces, Haeckel.
Mantle of the double cone compressed, with elliptical transverse section; its contour straight; its surface with numerous longitudinal furrows; its margin finely denticulated. Diameter of its mouth two-fifths as long as the whole shell and three times as broad as its equatorial diameter. The two main spines one-third longer than their conical sheath, four-edged. The eighteen smaller spines thick and short, cylindrical or a little compressed.
Dimensions.—Length of the shell 0.18; equatorial breadth 0.025, polar breadth 0.07.
Habitat.—Mediterranean (Messina), surface.
5. Diploconus cotyliscus, n. sp. (Pl. 140, fig. 4).
Mantle of the double cone compressed, thin walled, with elliptical transverse section; its contour convex; surface and margin nearly smooth. Diameter of its mouth half as long as the whole shell and twice as long as its equatorial diameter. The two main spines scarcely longer than their hemispherical sheath. The smaller spines conical, straight, nearly of the same length.
Dimensions.—Length of the shell 0.3; equatorial breadth 0.08, polar breadth 0.15.
Habitat.—Tropical Atlantic, Station 347, surface,
6. Diploconus saturnus, Haeckel.
Mantle of the double cone compressed, thick walled, with elliptical transverse section; its contour convex; its surface with numerous deep and irregular longitudinal furrows and marginal incisions. Diameter of its mouth one-third as long as the whole shell and twice as broad as its equatorial diameter. The two hydrotomical spines short, scarcely longer than their sheath. The eighteen other spines thin, cylindrical, nearly of the same length, curved. (Resembles a sheaf.)
Dimensions.—Length of the shell 0.24; equatorial breadth 0.04, polar breadth 0.07.
Habitat.—South Pacific, Station 300, surface.
7. Diploconus hexaphyllus, n. sp. (Pl. 140, fig. 2).
Mantle of the double cone compressed, thick walled, with elliptical transverse section; its contour straight; surface with six stronger and numerous smaller straight ribs and six marginal denticulate incisions. Diameter of its mouth one-third as long as the whole shell and somewhat smaller than the equatorial diameter. Hydrotomical spines about twice as long as their sheath, pyramidal, with emarginate point and six wings. Geotomical spines short and strong, pyramidal. Sixteen other spines thin, straight, conical.
Dimensions.—Length of the shell 0.3; equatorial breadth 0.11, polar breadth 0.1.
Habitat.—Central Pacific, Station 266, surface.
Genus 381. Diplocolpus,[11] n. gen.
Definition.—Diploconida with only two developed, very large spines (opposite in the hydrotomical axis); all the other eighteen spines quite rudimentary or externally atrophied.
The genus Diplocolpus is the last and the most modified genus among the Acantharia. The eighteen smaller spines of Diploconus are here quite rudimentary or have even perfectly disappeared by atrophy, so that the shell seems to consist only of the large hydrotomical spines and their enveloping sheaths.
Subgenus 1. Diplocolpulus, Haeckel.
Definition.—Mantle of the double cone not compressed; its transverse section therefore circular.
1. Diplocolpus costatus, n. sp. (Pl. 140, fig. 7).
Mantle of the double cone thin walled, not compressed; its transverse section circular or nearly hexagonal; its contour little convex; surface with six thick longitudinal equidistant ribs and many thinner ribs between them; margin denticulate. Transverse diameter of the shell one-third as long as the longitudinal. The two hydrotomical spines thick and short, little prominent over the polar mouth. No rudiments of other spines visible externally.
Dimensions.—Length of the shell 0.15; equatorial and polar breadth 0.05.
Habitat.—Indian Ocean (Madagascar), Rabbe, surface.
2. Diplocolpus cristatus, n. sp. (Pl. 140, fig. 6).
Mantle of the double cone thick walled, not compressed; its transverse section circular or hexagonal; its contour nearly straight; surface with six thick prominent longitudinal equidistant ribs; margin irregularly dentated. Transverse diameter of the shell half as long as the longitudinal. The two hydrotomical spines very thick and short, pyramidal, little prominent. Short rudiments of the eighteen other spines present, bristle-shaped.
Dimensions.—Length of the shell 0.1, breadth 0.05.
Habitat.—South Atlantic, Station 335, surface.
Subgenus 2. Diplocolpium, Haeckel.
Definition.—Mantle of the double cone compressed from both poles of the shortened geotomical axis; its transverse section therefore elliptical.
3. Diplocolpus serratus, n. sp. (Pl. 140, fig. 5).
Mantle of the double cone thick walled, compressed, with elliptical transverse section; its surface with numerous delicate ribs; contour little convex; margin regularly serrate. Hydrotomical spines short, pyramidal, with six serrate wings. Transverse diameter of the shell nearly twice as great at the polar mouth as at the equator and half as long as the whole shell.
Dimensions.—Length of the shell 0.15; breadth on the equator 0.035, on the poles 0.07.
Habitat.—Central Pacific, Station 274, surface.
4. Diplocolpus dentatus, n. sp. (Pl. 140, fig. 9).
Mantle of the double cone thin walled, compressed, with elliptical transverse section; its contour straight; surface with six deeper and numerous shallower furrows; margin denticulated, with six triangular prominent larger teeth. Hydrotomical spines very large prismatic, pyramidal at the ends. Transverse diameter of the shell a little larger at the polar mouth than at the equator and half as long as the whole shell.
Dimensions.—Length of the shell 0.2; breadth on the equator 0.08, on the poles 0.1.
Habitat.—North Pacific, Station 244, surface.
5. Diplocolpus sulcatus, n. sp. (Pl. 140, fig. 8).
Mantle of the double cone thin walled, compressed, with elliptical transverse section; its contour straight; surface with twelve to sixteen deep longitudinal furrows, which are separated by thin, undulating, double edged ribs; margin little dentated. Hydrotomical spines short, pyramidal, with six dentate wings. Transverse diameter of the shell a little larger at the polar mouth than at the equator, about one-third of the whole length of the shell.
Dimensions.—Length of the shell 0.17; breadth on the equator 0.05, on the poles 0.06.
Habitat.—South Pacific, Station 291, surface.
- ↑ Thoracaspis = Cuirass-shield; θώραξ, ἀσπίς.
- ↑ Belonaspis = Arrow-shield; βελόνη, ἀσπίς.
- ↑ Dictyaspis = Net-shield; δίκτυον, ἀσπίς.
- ↑ Coleaspis = Shield with sheaths; κολεός, ἀσπίς.
- ↑ Phatnaspis = Panel-shield or fretwork; φάτνη, ἀσπίς.
- ↑ Hexalaspis = Shield with six wings; ἕξαλος, ἀσπίς.
- ↑ Hexaconus = Shell with six cones; ἕξα, κῶνος.
- ↑ Hexonaspis = Shield with six auricles; ἕξονος, ἀσπίς.
- ↑ Hexacolpus = Shell with six bosoms; ἕξα, κόλπος.
- ↑ Diploconus = Double cone; διπλόος, κῶνος.
- ↑ Diplocolpus = Double bosom; διπλόος, κόλπος.