Dimensions.—Length of the cortical shell 0.16 to 0.18, breadth 0.12 to 0.14; thickness of the spongy wall 0.02; diameter of the medullary shell 0.04.
Habitat.—Pacific, central area, Station 268, depth 2900 fathoms.
3. Spongatractus streptacanthus, n. sp.
Cortical shell twice as long as broad, with thorny surface. Spongy framework loose, with large meshes, about as thick as the ellipsoidal medullary shell. Polar spines very long, three-sided prismatic, with three spirally contorted edges, much longer than the cortical shell, half as broad as the medullary shell.
Dimensions.—Length of the cortical shell 0.25, breadth 0.13; thickness of the spongy wall 0.03; diameter of the medullary shell 0.03 to 0.04.
Habitat.—North Atlantic, off Canary Islands, Haeckel.
Genus 150. Spongoliva,[[189]] n. gen.
Definition.—Spongurida with spongy ellipsoidal cortical shell, enclosing a double, spherical or ellipsoidal, latticed medullary shell. Polar spines absent.
The genus Spongoliva differs from the nearest Spongodruppa by duplication of the medullary shell; it bears therefore the same relation to this that Prunulum does to Druppula, and can be regarded as a Prunulum, in which the simple latticed cortical shell is replaced by a spongy framework.