Challengeron bethelli, John Murray, 1879, in litteris, Narr. Chall. Exp., vol. i. p. 226, pl. A, fig. 6.
Shell subcircular, lenticular, strongly compressed, with numerous (twenty to thirty) short conical spines on the margin (often wanting in the upper part of the dorsal margin). Peristome with a deep labial incision and two parallel triangular lateral teeth, the upper margin of which is horizontal.
Dimensions.—Diameter of the shell 0.2 to 0.25; length of the spines 0.02 to 0.03.
Habitat.—North Pacific, Stations 238, 241 (off Japan), depth between 2300 and 3950 fathoms.
20. Challengeron bathybium, n. sp.
Shell subcircular, lenticular, slightly compressed, with a corona of numerous (thirty to forty or more) short, conical, radial spines on the margin. Peristome helmet-shaped, nearly as long as the radius, with two widely divergent, conical, curved teeth, a vertical dorsal and a nearly horizontal ventral tooth.
Dimensions.—Diameter of the shell 0.22; length of the peristome 0.1.
Habitat.—Western Tropical Pacific, Station 225, depth 4475 fathoms.
21. Challengeron johannis, n. sp.
Shell ovate, slightly compressed, with a corona of numerous (forty to sixty or more) short radial spines on the margin, ten to fifteen of them (in the aboral half) are pyramidal, and much larger than the others. Peristome helmet-shaped, about one-third as long as the shell, with a deep bosom and two widely divergent teeth on the concave upper margin, a forked dorsal and a conical ventral.