Page:Scientific results HMS Challenger vol 18 part 2.djvu/832

1708 the middle third of the shell, diverge upwards, and are slightly arcuate, covered with numerous curved spines. Their base is pierced by four pedal pores. The peristome is a narrow sagittal fissure, placed in the radius of the odd or dorsal foot, and bears two opposite teeth on its two corners. The teeth are cylindrical, longer than the shell, covered with curved spines, and ascend in a parallel and vertical manner; each is perforated at the base by three large dental pores.

Dimensions.—Length of the shell 1.4, breadth 1.2.

Habitat.—North Pacific, Stations 244 to 250, depth 2050 to 3050 fathoms.

6. Tuscarora porcellana, John Murray (Pl. 100, figs. 6a, 6b).

Tuscarora porcellana, John Murray, 1819, in litteris, Narr. Chall. Exp., pl. A, fig. 18.

Shell pear-shaped, with three lateral perradial feet in the lower half of the shell, and two parallel vertical teeth on the mouth. The three lateral feet arise between the middle and the lower third of the shell, are straight, cylindrical, spinulate, about as long as the shell and diverge downwards; their base is pierced by four ovate pedal pores. The two parallel and vertical teeth are straight, shorter than half the shell, and opposite in the sagittal plane, on the two corners of the narrow mouth, in the radius of the dorsal odd foot. The base of each tooth exhibits four cordate dental pores.

Dimensions.—Length of the shell 1.5, breadth 1.3.

Habitat.—South Atlantic, Station 325, depth 2650 fathoms.

Definition.—Shell with three perradial equidistant feet, and with four crossed equidistant teeth around the mouth.

7. Tuscarora belknapii, John Murray.

Tuscarora belknapii, John Murray, 1879, in litteris, Narr. Chall. Exp., vol. i. p. 226, pl. A, figs. 15, 15a-15d.

Shell pear-shaped, with three lateral perradial feet in the upper third, and four crossed teeth around the mouth. The three arcuate feet are thin, cylindrical, covered with small curved thorns, and arise at the base of the peristome, between the upper and middle third of the shell; they ascend diverging to the height of the mouth, and are then curved downwards in a large arc, twice to three times as long as the shell. The base of each foot is dilated and pierced by three pedal pores. The four thin and long teeth of the peristome are similar to the feet, ascend in a slightly diverging manner, and are so placed that two opposite lie in the sagittal plane (or in the radius of the dorsal odd foot), whilst the two others are opposite in the frontal plane (perpendicular to the former). The base of each tooth exhibits two large ovate dental pores.

Dimensions.—Length of the shell 2.5, breadth 1.5.

Habitat.—South Pacific, Station 293, depth 2025 fathoms.