Subgenus 1. Dictyoplegma, Haeckel, 1862, Monogr. d. Radiol, p. 458.
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.
2. Spongodictyon cavernosum, n. sp.
Spongy framework of the cortical shell rather compact in the inner part, which immediately envelops the double medullary shell; very loose, with large caverns in the outer part, caverns of the surface larger than the medullary shell. Both medullary shells with regular circular pores, three times as broad as the bars.