6. Spongodiscus cycloides, Haeckel.
Spongy disk on both sides plain, in the central part with five to ten concentric, circular rings, in the peripheral part quite irregularly and densely spongy. Meshes twice to four times as broad as the bars.
Dimensions.—Diameter of the disk 0.1 to 0.2, of the meshes 0.003 to 0.006.
Habitat.—Mediterranean (Messina), North Atlantic (Canary Islands).
7. Spongodiscus spongocyclia, Haeckel.
Spongy disk lenticular, in the thicker central part with eleven to twelve circular, concentric rings, in the thinner, peripheral zone irregularly spongy. Meshes twice to four times as broad as the bars. (The triangular form in the specimen figured by Stöhr is accidental, produced by the broken margin.)
Dimensions.—Diameter of the disk 0.2 to 0.3, of the meshes 0.006 to 0.008.
Habitat.—Fossil in Tertiary rocks of Barbados (Haeckel) and Sicily (Stöhr).
Subgenus 3. Spongospira, Stöhr, 1880, Palæontogr., vol xxvi. p. 120.
Definition.—Spongy framework of the disk in the inner part with spiral convolutions, in the outer part irregular.
8. Spongodiscus florealis, Haeckel.
Spongy disk lenticular, in the thicker central part with five to six spiral convolutions, in the outer peripheral zone irregularly spongy. No radial beams piercing the framework. Meshes three to four times as broad as the bars.
Dimensions.—Diameter of the disk 0.26, of the meshes 0.006 to 0.008.
Habitat.—Fossil in Tertiary rocks of Sicily (Grotte), Stöhr.
9. Spongodiscus spiralis, n. sp.
Spongy disk on both sides plain, with twelve to sixteen spiral convolutions in the central part, with irregular, spongy framework in the outer part, pierced by numerous interrupted radial beams. Meshes five to six times as broad as the bars.
Dimensions.—Diameter of the disk 0.2 to 0.3, of the meshes 0.01 to 0.012.
Habitat.—Antarctic Ocean, Station 157, depth 1950 fathoms.
