Page:Scientific results HMS Challenger vol 18 part 1.djvu/559

Rh stout, conical, slightly sulcated, about as long as the breadth of the cortical shell, as broad at the base as the medullary shell.

Dimensions.—Length of the cortical shell 0.2, breadth 0.13; thickness of the spongy wall 0.045; diameter of the medullary shell 0.04.

Habitat.—Fossil in the rocks of Barbados, Ehrenberg; living in the Equatorial Atlantic, Station 348, depth (2450) fathoms.

2. Spongatractus fusiformis, n. sp.

Cortical shell one and a third times as long as broad, with nearly smooth surface. Spongy framework very compact, with very small meshes, about as thick as the radius of the spherical medullary shell. Polar spines very strong, three-sided pyramidal, about as long as the breadth of the cortical shell, as broad at the base as the medullary shell.

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.

Definition.— 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.

Definition.—Surface of the shell smooth or rough, without radial spines.