16. Heliodiscus marginatus, n. sp. (Pl. [34], fig. 9).
Disk with smooth surface, three times as broad as the medullary shell. Pores regular, circular; nine to ten on the radius. Equatorial girdle one-fourth to one-half as broad as the medullary shell, in the whole breadth radially striped, on the margin with twelve to eighteen very short and broad, triangular, marginal spines.
Dimensions.—Diameter of the disk 0.15 to 0.2, of the medullary shell 0.05 to 0.06; length of the marginal spines 0.01 to 0.02, basal breadth 0.02.
Habitat.—Central Pacific, Stations 265 to 268, depth 2900 fathoms.
17. Heliodiscus sulcatus, n. sp.
Disk with smooth surface, four times as broad as the medullary shell. Pores subregular, circular; twelve to fifteen on the radius. Equatorial girdle as broad as the medullary shell, in the whole breadth radially striped on the margin with ten to fifteen triangular, deeply sulcated teeth, about as long and broad as the medullary shell. (Similar to Heliodiscus glyphodon, Pl. [35], fig. 2, but with broad sulcated girdle and shorter, more numerous spines.)
Dimensions.—Diameter of the disk 0.15 to 0.2, of the medullary shell 0.04 to 0.05; length of the radial spines 0.05 to 0.06, basal breadth 0.04 to 0.05.
Habitat.—Atlantic and Pacific, tropical part, many Stations, surface.
18. Heliodiscus umbonatus, Haeckel.
Haliomma umbonatum, Ehrenberg, 1875, Abhandl. d. k. Akad. d. Wiss. Berlin, p. 74, Taf. xxvii. fig. 4.