Dimensions.—Diameter of the disk 0.2, of the medullary shell 0.06; length of the crossed spines 0.1, basal breadth 0.02.
Habitat.—Pacific, central area, Station 271, depth 2425 fathoms.
6. Sethostaurus coronatus, n. sp.
Disk with spiny surface, twice as broad as the medullary shell. Pores irregular, roundish; nine to ten on the radius. Margin of the disk with a solid broad girdle, bearing on the periphery a corona of thirty to forty flat tongue-shaped teeth of different length. Four crossed spines prismatic with prominent edges, about as long as the diameter of the disk, and as broad as the girdle.
Dimensions.—Diameter of the disk 0.16, of the medullary shell 0.08, length of the crossed spines 0.18, breadth 0.02.
Habitat.—Pacific, central area, Station 268, depth 2900 fathoms.
7. Sethostaurus gigas, n. sp.
Disk with smooth surface, four times as broad as the medullary shell. Pores regular, circular; twenty to twenty-two on the radius. Margin of the disk with a narrow solid girdle, bearing on the periphery one hundred to one hundred and twenty slender flat pointed teeth. Four crossed spines equal, conical, about as long as the radius of the disk, as broad at their furrowed base as the radius of the medullary shell.
Dimensions.—Diameter of the disk 0.4, of the medullary shell 0.1; length of the crossed spines 0.5, basal breadth 0.05.
Habitat.—Western Tropical Pacific, Station 225, depth 4475 fathoms.