Habitat.—Western Tropical Pacific, Station 224, depth 1850 fathoms.
11. Challengeron tizardi, John Murray.
Challengeria tizardi, John Murray, 1879, in litteris, Narr. Chall. Exp., vol i. p. 226, pl. A, figs. 7-7b.
Shell nearly equilateral triangular, with concave ventral, convex dorsal and aboral edges, on the two corners of the latter two opposite horizontal spines (a dorsal and a ventral). Peristome auriculate and bilobate, with a deep ventral incision on the base, and three pointed triangular teeth, the upper margins of which are nearly horizontal.
Dimensions.—Diameter of the shell 0.22 to 0.3, length and breadth of the peristome 0.01 to 0.12.
Habitat.—South Atlantic, Stations 332 to 335, depth 1425 to 2200 fathoms.
12. Challengeron triangulum, n. sp. (Pl. [99], fig. 10).
Shell nearly equilateral triangular, with three slightly convex or nearly straight sides, and two opposite obliquely descending and diverging spines on the two corners of the aboral margin. Peristome auriculate and bilobate, with a very thin basal neck and a deep incision on its ventral side; its distal margin is obliquely truncate, and exhibits an odd ascending dorsal tooth and two parallel, paired, descending, lateral teeth.
Dimensions.—Diameter of the shell 0.2 to 0.3; length and breadth of the peristome 0.1 to 0.12.
Habitat.—North Pacific, Stations 244 to 253, depth 2050 to 3125 fathoms.