Page:Scientific results HMS Challenger vol 18 part 1.djvu/558

350 Dimensions.—Length of the cortical shell 0.24, breadth 0.18; thickness of its wall 0.035; diameter of the medullary shell 0.06.

Habitat.—North Pacific, Station 244, depth 2900 fathoms.

5. Spongodruppa elliptica, Haeckel.

Acanthosphæra elliptica, Ehrenberg, 1872, Abhandl. d. k. Akad. d. Wiss. Berlin, p. 285, Taf. vii. fig. 4.

Cortical shell nearly twice as long as broad, four times as broad as the ellipsoidal medullary shell. Spongy framework compact, with small meshes. Surface covered with very numerous short radial spines, about as long as the medullary shell.

Dimensions.—Length of the cortical shell 0.2, breadth 0.11; length of the medullary shell 0.04, breadth 0.03.

Habitat.—Philippine Sea, Ehrenberg, Station 206, depth 2100 fathoms.

6. Spongodruppa polyacantha, Haeckel.

Haliomma polyacanthum, J. Müller, 1858, Abhandl., p. 36, Taf. i. figs. 10, 11.

Haliomma polyacanthum, Haeckel, 1862, Monogr. d. Radiol., p. 430.

Cortical shell one and a third times as long as broad, twice as broad as the ellipsoidal medullary shell. Spongy framework loose on the surface, with large regular meshes. Surface covered with fifteen to twenty thick, conical spines, about as long as the radius of the shell.

Dimensions.—Length of the cortical shell 0.12, of the medullary shell 0.09; diameter of the medullary shell 0.05 to 0.06.

Habitat.—Mediterranean (south coast of France); Atlantic (Canary Islands), Station 354, surface.

Definition.— 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