Phacoid shell three times as broad as the medullary shell, with six to eight pores on its radius, surrounded by one perfect chambered ring. Arms nearly trapezoidal, about as long as the diameter of the central disk, at the base half as broad, at the truncated distal end nearly as broad as long, and armed with a large pyramidal terminal spine. Each arm with about eight transverse and longitudinal rows of chambers.
Dimensions.—Diameter of the phacoid shell 0.11, of the medullary shell 0.04; length of the arms 0.1, basal breadth 0.05, distal breadth 0.09.
Habitat.—Cosmopolitan; Atlantic, Indian, Pacific, at various depths; fossil in the Tertiary rocks of Barbados and Nicobar.
4. Astractura democriti, n. sp.
Astromma aristotelis, var., Ehrenberg, 1875, Abhandl. d. k. Akad. d. Wiss. Berlin, p. 66, Taf, xxx. fig. 3.
? Astromma aristotelis, var., Bury, 1862, Polycystins of Barbados, pl. xiv. fig. 4.
Phacoid shell twice as broad as the medullary shell, with five to seven pores on its radius, without perfect chambered ring. Arms about twice as long as broad, longer than the diameter of the central disk, at the truncated distal end a little broader than at the base, and armed with a strong, pyramidal, terminal spine.
Dimensions.—Diameter of the phacoid shell 0.1, of the medullary shell 0.05; length of the arms 0.15, basal breadth 0.04, distal breadth 0.08.
Habitat.—Pacific, central area, Station 266, depth 2750 fathoms; fossil in Barbados.
5. Astractura hippocratis, n. sp.