Habitat.—Indian Ocean, Cocos Islands (Rabbe), surface.
Genus 681. Sagoplegma,[[300]] n. gen.
Definition.—Sagosphærida with a spongy spherical shell, the thickened wall of which is composed of a loose spongy framework, and bears on its surface numerous pyramidal elevations.
The genus Sagoplegma differs from Sagmarium, its ancestral form, in the development of pyramidal or tent-shaped elevations on the surface of the spongy hollow sphere. It exhibits, therefore, the same relation to the latter as the similar Sagoscena bears to Sagena. The wall of the spherical shell is in the two latter genera a thin simple lattice-plate, in the former a thickened spongy framework.
1. Sagoplegma pyramidophora, n. sp.
Pyramids on the surface of the spongy sphere subregular, mostly tetrahedral, of nearly equal size and similar form. The three edges of each pyramid are prolonged over its top into three short, divergent, apical spines which are forked at the distal end. (Very similar to Sagoscena castra and Sagoscena tentorium, Pl. [108], figs. 1, 6, probably derived from them, but differing in the spongy structure of the thickened shell-wall, which is half as thick as the radius of its cavity.)
Dimensions.—Diameter of the sphere 2.0 to 2.5, length of the bars 0.15 to 0.2, breadth 0.002.
Habitat.—North Pacific, Stations 231 to 239, surface.
2. Sagoplegma scenophora n. sp. (Pl. [108], fig. 13).
Pyramids on the surface of the spongy sphere irregular, with three to six sides, unequal in size and different in form. The edges of each pyramid are prolonged over its top into three to six divergent apical spines, which bear three to six cruciate verticils, each composed of four small, crossed, lateral branches, armed with a spinulate knob at the distal end.