The genus Spongostylus may probably be derived from Spongoplegma by development of two opposite radial spines in one axis.
1. Spongostylus hastatus, n. sp.
Spongy cortical shell with compact framework, twice as broad as the enclosed medullary shell, the pores of which are regular, circular, twice as broad as the bars. Two polar spines, three times as long as the radius of the shell, in the basal two-thirds cylindrical, in the distal third compressed, two-edged, spear-shaped.
Dimensions.—Diameter of the cortical shell 0.1, medullary shell 0.05; length of the spines 0.15.
Habitat.—South Atlantic, Station 335, depth 1425 fathoms.
2. Spongostylus gladiatus, Haeckel.
Stylosphæra holosphæra, Ehrenberg, 1872, Abhandl. d. k. Akad. d. Wiss. Berlin, p. 299, Taf. viii. fig. 14.
Spongy cortical shell with rather compact framework, four times as broad as the enclosed medullary shell, the pores of which are irregular, roundish, three to four times as broad as the bars. Two polar spines sword-shaped, two-edged, as long as the shell diameter.
Dimensions.—Diameter of the cortical shell 0.24, medullary shell 0.06; length of the spines 0.25.
Habitat.—Central Pacific, Station 268, depth 2900 fathoms; Philippine Sea, depth 3300 fathoms.