Genus 149. Spongatractus,[[188]] n. gen.
Definition.—Spongurida with spongy ellipsoidal cortical shell, enclosing a simple, spherical or ellipsoidal, latticed medullary shell. On the poles of the axis occur two opposite strong spines.
The genus Spongatractus differs from Spongodruppa by development of two strong spines in the axis of the shell, on its two opposite poles; therefore it bears the same relation to the latter that Lithatractus does to Druppula, and can be derived from Lithatractus by a spongy thickening of the cortical shell.
1. Spongatractus pachystylus, Haeckel.
Spongosphæra pachystyla, Ehrenberg, 1875, Abhandl. d. k. Akad. d. Wiss. Berlin, p. 82, Taf. xxvi. fig. 3.
Cortical shell one and a half times as long as broad, with rough surface. Spongy framework compact, with small meshes, about as thick as the spherical medullary shell. Polar spines very 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.