16. Challengeria trigona, Haeckel.
Challengeria macleari, var., John Murray, 1879, in litteris, Narr. Chall. Exp., vol. i. p. 226, pl. A, fig. 3b.
Shell triangular, with three rounded corners; the two lateral sides nearly straight, equal, the aboral side more or less convex and somewhat shorter. Peristome a curved half-tube (often longer than in Murray's figure), one-third to one-half as long as the shell, with three short triangular diverging and ascending teeth of equal length.
Dimensions.—Length of the shell 0.25 to 0.3, breadth 0.2 to 0.25; length of the peristome 0.08 to 0.12.
Habitat.—South Atlantic, Stations 332 to 335, depth 1425 to 2200 fathoms.
17. Challengeria trifida, n. sp.
Shell ovate, more or less compressed, about two-thirds as long as broad. Peristome semitubular, obliquely ascending, about one-third as long as the shell, in the lower half simple, in the upper trifid, with three curved divergent teeth; the dorsal odd tooth shorter than the paired lateral teeth.
Dimensions.—Length of the shell 0.3 to 0.36, breadth 0.24 to 0.28.
Habitat.—South Pacific, Station 289, depth 2550 fathoms.