Definition.—Spongurida with ellipsoidal or cylindrical shell of solid spongy framework, without internal cavity and without latticed medullary shell. On the poles of the axis occur two opposite strong spines.
The genus Spongoprunum differs from the most nearly allied Spongurus by the possession of two strong solid spines, lying in the axis of the ellipsoidal or cylindrical massive spongy shell, on its two opposite poles. Spongoprunum bears therefore the same relation to Spongurus that Ellipsoxiphus does to Cenellipsis.
1. Spongoprunum amphilonche, n. sp. (Pl. [48], fig. 7).
Shell ellipsoidal, two and a third times as long as broad, with nearly smooth surface. Spongy framework very compact, in the whole solid shell of the same structure, with very small meshes, 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.