Dimensions.—Diameter of the shell 0.22, pores 0.02 to 0.04, bars 0.01; length of the spines 0.04, basal breadth 0.01.
Habitat.—Central Pacific, Station 271, depth 2425 fathoms.
Genus 89. Heliosphæra,[[123]] Haeckel, 1862, Monogr. d. Radiol., p. 350 (sensu emendato).
Definition.—Astrosphærida with one simple lattice-sphere, covered with simple radial spines of two different kinds: larger main spines and smaller by-spines.
The genus Heliosphæra (in the mended definition here employed) differs from the foregoing Acanthosphæra in the possession of two different kinds of radial spines: larger main spines scattered on the surface or disposed regularly in limited numbers (twelve to twenty, sometimes forty to fifty or more), and smaller by-spines in much larger numbers, arising from all the nodal-points of the network (or sometimes also from its bars).
Subgenus 1. Heliosphærella, Haeckel.
Definition.—Pores of the shell regular or subregular, all of nearly equal size and similar form.
1. Heliosphæra hexagonaria, n. sp. (Pl. [26], fig. 2).
Shell very thin walled, about twenty times as broad as one pore. Meshes or pores subregular, hexagonal, with thread-like bars; fifteen to seventeen on the radius. Radial spines at the nodal-points of the network; about forty main spines three-sided pyramidal, half as broad at the base as one pore, and twice as long as the bristle-shaped by-spines, which are very numerous, and as long as the diameter of one pore.
Dimensions.—Diameter of the shell 0.25 to 0.3, of the meshes or pores 0.012 to 0.015, bars below 0.001; length of the main spines 0.03, basal breadth 0.007.