Page:Scientific results HMS Challenger vol 18 part 1.djvu/487

Rh Dimensions.—Diameter of the sphere 0.9, of the central cube 0.02; length of the spines 0.15, distal thickness 0.02.

Habitat.—South Pacific, Station 295, surface.

Definition.— with a single, cubical medullary shell, and eight primary radial spines arising from its eight corners; these are connected at equal distances by a latticed, spherical, cortical shell, from which the spongy framework directly springs; often from the latter secondary radial spines arise.

The genus Octodendron has the same regular, cubical medullary shell as the preceding Centrocubus, but differs from it in the wide interval separating the medullary shell from the inner spherical face of the spongy cortical shell, the two being connected only by eight radial beams, arising from the eight corners of the cube.

Definition.—Only eight primary radial spines, arising from the eight corners of the central cube.

1. Octodendron cubocentron, n. sp. (Pl. 18, fig. 3).

Radial spines eight, club-shaped, with three denticulate, straight edges, twice as long as the diameter of the central cavity of the cubical spongy shell; the inner face of the latter (or the "inner cortical shell") exhibits the form of a large cube, the spongy sides of which are parallel with the simple square sides of the central cube. The thin eight radial beams, connecting the corresponding corners of both cubes, are not thicker than the edge-bars of the central cube, whilst their outer prolongations are much thicker, with four to six verticils of lateral branches. Surface of the thin walled, loose, spongy shell armed with short simple thorns.

Dimensions.—Diameter of the spongy shell 0.2, of its inner cavity 0.1, of the central cube 0.02; length of the spines 0.2 (from the centre 0.3).

Habitat.—Central Pacific, Station 266, surface.

2. Octodendron spirale, n. sp.

Radial spines eight, three-sided prismatic, three times as long as the diameter of the inner shell-cavity; their three edges denticulated and spirally contorted around the spine axis. Thickness of the loose spongy shell-wall equal to the radius of the inner cavity, three times as large as the central cube. Surface covered, with numerous thin, bristle-shaped, bent spinules.