Disk with smooth surface, four times as broad as the medullary shell. Pores regular, circular; about ten on the radius of the disk. Eight marginal spines regularly distributed (sometimes seven or nine, more or less irregular), angular, nearly pyramidal (with equilateral triangular outline), about as long and broad as the diameter of the medullary shell, without connecting equatorial girdle. From the broad base of each spine run eight to ten deep furrows convergent to its apex.
Dimensions.—Diameter of the disk 0.2, of the medullary shell 0.05; length of the radial spines 0.05, basal breadth 0.05.
Habitat.—North Pacific, Station 266, surface.
2. Heliosestrum octastrum, n. sp.
Disk with smooth surface, three times as broad as the medullary shell. Pores irregular, roundish; eight to nine on the radius. Eight marginal spines regularly distributed (sometimes seven or nine, more or less irregular), conical, about as long as the diameter of the disk, without a connecting equatorial girdle.
Dimensions.—Diameter of the disk 0.15, of the medullary shell 0.05; length of the radial spines 0.16, basal breadth 0.01.
Habitat.—Pacific, central area, Station 271, depth 2425 fathoms.
3. Heliosestrum solarium, Haeckel.
Haliomma sol (partim), Ehrenberg, 1875 (non 1844), Abhandl. d. k. Akad. d. Wiss. Berlin, p. 74, Taf. xxviii. fig. 1.
Surface of the disk smooth; its diameter six times as large as that of the medullary shell. Pores regular, circular; nine to ten on the radius. Eight marginal spines regularly distributed (sometimes seven or nine, more or less irregular), conical, about as long as the diameter of the medullary shell, without a connecting equatorial girdle.