Page:Scientific results HMS Challenger vol 18 part 1.djvu/357

Rh

Definition.— with a solid sphere of spongy framework, and with two opposite free radial spines.

The genus Spongolonchis differs from its probable ancestral form, Styptosphæra, by the development of two opposite radial spines situated in one axis.

1. Spongolonchis compacta, n. sp.

Spongy framework of the spherical shell very compact, with small meshes, three to four times as broad as the bars. Surface rough, but not spiny. Two polar spines pyramidal, only as long as the radius of the shell, one-third as broad at the base.

Dimensions.—Diameter of the shell 0.2; length of the spines 0.1, basal breadth 0.03.

Habitat.—Central Pacific, Station 274, depth 2750 fathoms.

2. Spongolonchis laxa, n. sp.

Spongy framework loose, with large meshes, ten to twelve times as broad as the bars. Surface spiny. Two polar spines three-sided prismatic, longer than the diameter of the shell (broken off in the observed specimen).

Dimensions.—Diameter of the shell 0.5; length of the spine 0.6 and more, breadth 0.02.

Habitat.—Central Pacific, Station 265, depth 2900 fathoms.

Definition.— with spongy spherical cortical shell, enclosing in the centre a simple latticed medullary shell, and with two opposite free radial spines.

The genus Spongostylus may probably be derived from Spongoplegma by development of two opposite radial spines in one axis.

1. Spongostylus hastatus, n. sp.

Spongy cortical shell with compact framework, twice as broad as the enclosed medullary shell, the pores of which are regular, circular, twice as broad as the bars. Two polar spines, three times as long as the radius of the shell, in the basal two-thirds cylindrical, in the distal third compressed, two-edged, spear-shaped.

Dimensions.—Diameter of the cortical shell 0.1, medullary shell 0.05; length of the spines 0.15.

Habitat.—South Atlantic, Station 335, depth 1425 fathoms.