16. Challengeria trigona, Haeckel.
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.
Subgenus 4. Challengeromma, Haeckel.
Definition.—Peristome with four to six or more teeth.
18. Challengeria quadridens, n. sp.
Shell subglobose, with nearly circular perimeter. Peristome an oblique short and broad tube, the breadth of which is twice as great as its length and equal to the radius of the shell. Margin of the peristome with four divergent, short, triangular teeth, the two dorsal teeth half as long as the two ventral.
Dimensions.—Diameter of the shell 0.22 to 0.24, breadth of the peristome 0.1.
Habitat.—Central Pacific, Stations 265 to 268, depth 2700 to 2900 fathoms.
19. Challengeria bromleyi, n. sp. (Pl. 99, fig. 3).
Shell ovate, lenticular, strongly compressed. Peristome a broad, trapezoidal, horizontal lamella, the breadth of which is twice as great as its length and nearly equal to the diameter of the shell; its margin with four divergent triangular lamellar teeth, the two dorsal teeth three times as long as the two ventral.
Dimensions.—Length of the shell 0.08 to 0.1, breadth 0.05 to 0.07; breadth of the peristome 0.08.
Habitat.—North Pacific, Stations 244 to 253, surface, and in various depths.
