Page:Scientific results HMS Challenger vol 18 part 1.djvu/425

Rh irregular, polygonal pores; twenty to thirty on the radius. Radial spines very numerous, bristle-shaped, twice to three times as long as the diameter of the pores.

Dimensions.—Diameter of the shell 0.3, pores 0.01 to 0.02; length of the spines 0.02 to 0.05.

Habitat.—Central Pacific, Station 274, surface.

31. Acanthosphæra reticulata, n. sp. (Pl. 26, fig. 5).

Rhaphidosphæra reticulata, Haeckel, 1881, Prodromus.

Shell thick walled, with irregular, roundish pores, twice to four times as broad as the bars; six to eight on the radius. Surface of the bars covered with a peculiar delicate network of very fine crests. Twenty to forty radial spines, angular, pyramidal, scarcely one-third as long as the radius of the shell, as broad at the base as the bars.

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.

Definition.— 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).

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.