Page:Scientific results HMS Challenger vol 18 part 2.djvu/810

1686 8. Castanidium moseleyi, n. sp. (Pl. 113, fig. 2).

Pores irregular, roundish or polygonal, two to four times as broad as the bars. Bristles about as long as the diameter of one pore, or a little longer. Radial main-spines cylindrical, irregularly curved, somewhat longer than the diameter of the shell; their base is more or less inflated and fenestrated, therefore the shell is nearly polyhedral.

Dimensions.—Diameter of the shell 0.7 to 0.8, of the pores 0.01 to 0.04.

Habitat.—Tropical Atlantic, Stations 346 to 349, surface.

Definition.— with simple radial main-spines and a dentate mouth.

The genus Castanissa agrees with the preceding Castanidium in the possession of large radial main-spines, scattered between the numerous bristles or by-spines of the surface; but it differs from it in the possession of teeth around the mouth, identical with those of Castanella; it may be derived therefore either from the latter by development of main-spines, or from the former by formation of teeth.

1. Castanissa challengeri, n. sp. (Pl. 113, fig. 1).

Pores regular, circular, three times as broad as the bars. Bristles one-fourth as long as the radius. Radial main-spines (about twelve) very stout, straight, cylindrical, at the distal end conical, pointed, with dimpled surface, about half as long as the radius. Mouth very large, circular, about one-third as broad as the shell, with a corona of twelve to sixteen very large, triangular, parallel teeth.

Dimensions.—Diameter of the shell 0.7 to 0.8, of the pores 0.03.

Habitat.—Tropical Atlantic, Station 347, depth 2250 fathoms.

2. Castanissa pearceyi, n. sp.

Pores regular, circular, twice as broad as the bars. Bristles half as long as the radius. Radial main-spines (about twenty) slender, cylindrical, smooth, irregularly curved, about as long as the radius. Mouth large, half as broad as the radius, with a corona of ten to twelve irregular, slender teeth.

Dimensions.—Diameter of the shell 0.5 to 0.6, of the pores 0.02.

Habitat.—South Atlantic, Station 332, depth 2200 fathoms.