Page:Scientific results HMS Challenger vol 18 part 2.djvu/777

Rh 20. Challengeria wildi, n. sp. (Pl. 99, fig. 2).

Shell subspherical, slightly compressed. Peristome semitubular, curved, as long as the shell-radius; with five curved lamellar teeth, an odd longer dorsal tooth and two pairs of lateral teeth.

Dimensions.—Diameter of the shell 0.12 to 0.18, length of the peristome 0.08 to 0.12.

Habitat.—Tropical Atlantic, Stations 347 to 348, depth 2250 to 2450 fathoms.

21. Challengeria aldrichi, John Murray, Challengeria aldrichi1876, L. N. 27, pl. 24, fig. 2.

Challengeria aldrichi, John Murray, 1879, in litteris, Narr. Chall. Exp., vol. i. p. 226, pl. A, fig. 4.

Shell subspherical, slightly compressed. Peristome a collar-like curved lamella, the breadth of which is twice as great as its length, and equals the radius of the shell; its margin with six short triangular teeth, two convergent ventral, two external horizontal lateral, and two ascending dorsal.

Dimensions.—Diameter of the shell 0.2, breadth of the peristome 0.1.

Habitat.—North Pacific, Station 244 to 248, depth 2050 to 2900 fathoms.

22. Challengeria murrayi, n. sp. (Pl. 99, fig. 1).

Shell subcircular, lenticular, strongly compressed. Peristome a trapezoidal, curved, collar-like lamella, the breadth of which is three times as great as its length and equal to the diameter of the shell; its margin with six triangular teeth, disposed like the preceding species, but larger.

Dimensions.—Diameter of the shell 0.15, breadth of the peristome 0.15.

Habitat.—North-Western Pacific (south of Japan), Station 231, depth 2250 fathoms.

Definition.— without pharynx, with one or more teeth on the mouth, and with marginal spines.

The genus Challengeron has in general the same shape as the preceding closely allied Challengeria, but differs from it in the development of radial spines on the sagittal margin of the shell, which in the latter genus is smooth. According to the different number and arrangement of these marginal spines, which give a very singular appearance to them, we divide the twenty-five species of this cosmopolitan genus into four subgenera:—(1) with a single, odd apical spine; (2) with two opposed aboral spines (a dorsal and a ventral); (3) with a bunch of aboral spines; (4) with numerous radial spines along the whole sagittal margin of the shell.

Definition.—Margin of the shell with a single spine on the apical pole, opposite to the peristome (Challengeriæ caudatæ).