Page:Scientific results HMS Challenger vol 18 part 1.djvu/298

90 The genus Spongoplegma may be regarded as a Carposphæra, in which the simple latticed cortical shell is represented by an irregular spongy framework, immediately enclosing the simple latticed medullary shell.

1. Spongoplegma antarcticum, n. sp.

Cortical shell with loose spongy framework and rough surface, four to six times as broad as the enclosed simple medullary shell. Pores of the latter regular circular, twice as broad as the bars. From its surface arise numerous (forty to fifty or more) short radial beams, which become forked and compose, by communication of lateral branches, the spongy cortical shell.

Dimensions.—Diameter of the spongy cortical shell 0.2 to 0.3 of the latticed medullary shell 0.05 to 0.06.

Habitat.—Antarctic Ocean, in large number, together with Cromyosphæra antarctica; in the Diatom ooze of Station 157 (depth 1950 fathoms).

Definition.— forming a sphere of spongy framework, which encloses in the centre a double latticed concentric medullary shell.

The genus Spongodictyon can be regarded as a Thecosphæra, in which the simple latticed cortical shell is represented by an irregular spongy framework, which immediately encloses the double latticed medullary shell. Sometimes this latter appears triple, the inner surface of the spongy cortical shell forming a smooth spherical lattice-plate, separated by an interval from the double medullary shell.

Definition.—Spongy cortical shell enveloping immediately the double medullary shell.

1. Spongodictyon spongiosum, Haeckel.

Dictyosoma spongiosum, J. Müller, 1858, Abhandl. d. k. Akad. d. Wiss. Berlin, p. 31, Taf. ii. figs. 9-11.

Dictyoplegma spongiosum, Haeckel, 1862, Monogr. d. Radiol., p. 458.

Spongy framework of the cortical shell loose, with large, polygonal roundish meshes, on an average as large as the double medullary shell, which is immediately enveloped by it. Both concentric medullary shells with subregular roundish pores, twice as broad as the bars.

Dimensions.—Diameter of the cortical shell 0.2 to 0.3 or more; of the outer medullary shell 0.03, inner 0.01.

Habitat.—Mediterranean (French south coast, surface), J. Müller.