Spongy cortical shell with a very loose framework; on the surface are innumerable thin, forked, or repeatedly dichotomous by-spines. Its inner cavity three times as broad as the medullary shell, which exhibits regular, hexagonal meshes (fig. 9a). Radial spines twelve, prismatic, with straight dentated edges, their outer pointed part as long as the shell radius. Each spine between the two shells has a verticil of three forked lateral branches (fig. 9a). The central capsule completely distends the medullary shell, and forces out through each mesh a hernia-shaped process (fig. 9).
Dimensions.—Diameter of the spongy shell 0.5, of its inner cavity 0.25, of the medullary shell 0.08.
Habitat.—Central Pacific, Station 271, surface.
5. Rhizoplegma lychnosphæra, n. sp. (Pl. [11], fig. 5).
Lychnosphæra rhizoplegma, Haeckel, 1879, Atlas (pl. xi. fig. 5).
Spongy cortical shell with a very loose framework, composed of long thin beams as in Lychnosphæra regina (Pl. [11], figs. 1-4). Surface covered with short bristles. Its inner cavity six times as broad as the medullary shell, which exhibits regular, hexagonal meshes. Radial spines twelve, prismatic, with three smooth edges; their outer pointed part half as long as the shell radius. Each spine has three verticils of three forked branches; the first verticil is free between the two shells, while the two following verticils, by communication of their ramules, form the irregular framework. Central capsule with many herniæ, forced out through the meshes of the medullary shell (fig. 5).
Dimensions.—Diameter of the spongy shell 0.7, of its inner cavity 0.45, of the medullary shell 0.07.
Habitat.—South Pacific, Station 284, surface.
Genus 117. Lychnosphæra,[[156]] Haeckel, 1881, Prodromus, p. 453.
Definition.—Astrosphærida with a single, spherical, latticed medullary shell, which is armed with free radial by-spines, and connected by stout radial main spines with the spongy cortical shell.