Page:Scientific results HMS Challenger vol 18 part 2.djvu/510

1386 The genus Clathrocyclas differs from the preceding closely allied Calocyclas in the dilated mouth and the flatter form of the abdomen, which is usually truncate, conical, or nearly discoidal. The conical thorax is often separated from the flat abdomen by an elegant ribbon of small quadrangular pores. The feet or teeth of the terminal corona are divergent, or even horizontally expanded, whilst in Calocyclas they are usually vertical or somewhat convergent.

Definition.—Shell highly conical, often ovate or slenderly campanulate. Cephalis commonly with a single horn.

1. Clathrocyclas principessa, n. sp. (Pl. 74, fig. 7).

Shell ovate, with two distinct strictures. Length of the three joints = 1 : 2 : 1, breadth = 1 : 2 : 2. Cephalis hemispherical, large, with a pyramidal, occipital horn of the same length. Thorax subspherical, with irregular, circular pores, about as broad as the bars. Abdomen short, widely open with a single transverse row of circular pores, and a coronal of twelve triangular, divergent feet, as long as the abdomen.

Dimensions.—Length of the three joints, a 0.03, b 0.06, c 0.03; breadth, a 0.04, b 0.08, c 0.09.

Habitat.—Central Pacific, Station 265, depth 2900 fathoms.

2. Clathrocyclas basilea, (Pl. 74, fig. 6).

Shell campanulate, with two deep strictures. Length of the three joints = 2 : 5 : 3, breadth = 3 : 7 : 9. Cephalis hemispherical, with an ovate, oblique horn of the same length. Thorax hemispherical, with subregular, circular pores of the same breadth as the bars. Abdomen short, with two transverse rows of the same pores, and with a coronal of sixteen to twenty ovate, divergent feet, as long as the horn.

Dimensions.—Length of the three joints, a 0.02, b 0.05, c 0.03; breadth, a 0.035, b 0.07, c 0.09.

Habitat.—Tropical Atlantic, Station 348, depth 2450 fathoms.

3. Clathrocyclas fimbriata, Haeckel.

? Halicalyptra fimbriata, Ehrenberg, 1875, Abhandl. d. k. Akad. d. Wiss. Berlin, p. 72, Taf. ii. fig. 11.

Shell campanulate, with two deep strictures. Length of the three joints = 1 : 3 : 1, breadth = 1 : 3 : 5. Cephalis hemispherical, with a conical horn of twice the length. Thorax hemispherical, in the upper half hyaline, without pores, in the lower half with four to six transverse rows of subregular, circular pores. Abdomen short, suddenly dilated, with one or two transverse rows of larger