Habitat.—Fossil in Tertiary rocks of Greece (Ægina), Ehrenberg.
7 Heliodiscus siculus, Stöhr.
Heliodiscus siculus, Stöhr, 1880, Palæontogr., vol. xxvi. p. 89, Taf. i. fig. 14.
Disk with smooth surface, three times as broad as the medullary shell. Pores irregular roundish; seven to eight on the radius. Marginal spines forty to fifty, conical, very irregular, the largest as long as the radius of the medullary shell, their bases coming in contact.
Dimensions.—Diameter of the disk 0.13 to 0.15, of the medullary shell 0.04 to 0.05; length of the radial spines 0.02 to 0.03, basal breadth 0.002 to 0.006.
Habitat.—Fossil in Tertiary rocks of Sicily, Grotte (Stöhr), Caltanisetta (Teuscher).
8. Heliodiscus polymorphus, n. sp. (Pl. [34], figs. 11, 12).
Disk with smooth surface, four times as broad as the medullary shell. Pores irregular, roundish; ten to twelve on the radius. Marginal spines ten to fifteen, pyramidal, angular, very irregular and variable in size and distribution, the largest nearly as long as the diameter of the disk, as broad at the base as the radius of the medullary shell.
Dimensions.—Diameter of the disk 0.15 to 0.2, of the medullary shell 0.04 to 0.05; length of the radial spines 0.06 to 0.18, basal breadth 0.02 to 0.03.
Habitat.—Central Pacific, Stations 265 to 268, depths 2700 to 2900 fathoms.