Page:Scientific results HMS Challenger vol 18 part 1.djvu/556

348 scarcely broader than the bars. Two polar spines conical, very strong, about half as long as the main axis of the shell and three times as long as broad.

Dimensions.—Length of the shell (without spines) 0.2, breadth 0.08.

Habitat.—Central Pacific, Station 265, depth 2900 fathoms; fossil in the rocks of Barbados.

2. Spongoprunum atractus, n. sp.

Shell spindle-shaped, twice as long as broad, with thorny surface. Spongy framework loose, in the whole shell of the same structure, with large meshes, eight to twelve times as broad as the bars. Two polar spines angular, pyramidal, very strong, about one-third as long as the shell, and twice as long as broad.

Dimensions.—Length of the shell 0.2, breadth 0.11.

Habitat.—Western Tropical Pacific, Station 225, depth 4475 fathoms.

3. Spongoprunum amphicylindrus, n. sp.

Shell nearly cylindrical, four times as long as broad, with rough surface. Spongy framework compact, in the whole shell of equal structure, with small meshes, twice to three times as broad as the bars. Two polar spines cylindrical, very large, longer than the shell, and about one-fourth as thick as its diameter.

Dimensions.—Length of the shell 0.2, breadth 0.05.

Habitat.—South Atlantic, Station 333, surface.

Definition.— with latticed medullary shell, enclosed by a spongy cortical shell.

Definition.— with spongy ellipsoidal cortical shell, enclosing a simple, spherical or ellipsoidal, latticed medullary shell. Polar spines absent.

The genus Spongodruppa opens the series of Spongodruppida, or of those Spongurida in which the ellipsoidal spongy cortical shell encloses a simple or double, latticed, medullary shell. In Spongodruppa, the simplest and probably the ancestral form of this subfamily, the medullary shell is simple and the polar spines absent. It may be derived from Druppula by a spongy thickening of the simple latticed cortical shell.