innumerable short, bristle-shaped radial spines, only one-eighth as long as the radius, of the same elegant form as in Octodendron spathillatum (Pl. 18, figs. 2, 4); each spine developed in a zig-zag fashion, with very small beards, with a delicate spathillum (or coronal of beard spines) at the distal end.
Dimensions.—Diameter of the spheres 0.16; length of the spines 0.01.
Habitat.—South Pacific, Station 295, surface.
4. Spongiomma clavatum, n. sp.
Spongy framework in the central part of the sphere much denser and darker than in the peripheral part. On the surface are sixty to eighty stout, club-shaped radial spines, as long as the radius of the sphere, in the proximal half three-sided prismatic, with three dentated edges; they begin at the middle of the radius (where the denser inner framework changes into the looser outer) and are very thin at first but increase slowly in thickness towards the truncated distal end. (Similar to Centrocubus rhopalophorus, Pl. 18, fig. 1, but without the cubical medullary shell.)
Dimensions.—Diameter of the sphere 0.4; length of the spines 0.2.
Habitat.—North Pacific, Station 241, surface.
Subgenus 2. Spongiommura, Haeckel.
Definition.—Radial spines on the surface of the spongy sphere of two different kinds; large main spines and small by-spines.
5. Spongiomma helioides, n. sp.
Spongy framework of the sphere everywhere of the same structure, with almost equal meshes, ten to twelve times as broad as the bars. Sixteen to twenty radial main spines, longer than the shell diameter, three-sided prismatic, with three serrated edges, beginning about the middle of the radius and increasing in thickness to the truncated distal end. Between them occur numerous thin, bent, bristle-shaped by-spines. (Very similar to Spongosphæra helioides, Monogr. d. Radiol., Taf. xii. figs. 11-13, but without medullary shells.)
Dimensions.—Diameter of the sphere 0.3; length of the main spines 0.4, of the by-spines 0.01.
Habitat.—Tropical Atlantic, Station 352, surface.
6. Spongiomma multiaculeum, Haeckel.
Spongy framework of the sphere very compact, with small meshes, scarcely broader than the bars; four to eight large main spines, three-sided pyramidal, longer than the shell radius; numerous (thirty to forty) thin by-spines, scarcely half as long.
