Page:Scientific results HMS Challenger vol 18 part 2.djvu/500

1376 circular, half as broad in the cephalis as in the two other joints. Thorax campanulate. Abdomen truncate, with eighteen to twenty-four parallel, vertical, longitudinal ribs, which are prolonged into slender, free, conical feet of the same length. (This remarkable species may be derived from Carpocanium by apposition of a third joint.)

Dimensions.—Length of the three joints, a 0.03, b 0.05, c 0.04; breadth, a 0.03, b 0.06, c 0.05.

Habitat.—Fossil in Barbados.

Definition.— (vel Tricyrtida multiradiata aperta) with four to six or more radial ribs in the abdomen, the terminal mouth of which is truncate, without feet.

The genus Cycladophora differs from the preceding Alacorys, its probable ancestral genus, in the absence of free terminal feet, the radial ribs of the abdomen being connected by transverse beams throughout their whole length. The number of the regularly disposed ribs (four to six or more) may also here be used for the distinction of different subgenera.

Definition.—Abdomen with four radial ribs, opposite in pairs in two meridian planes, perpendicular one to another.

1. Cycladophora gœtheana, n. sp. (Pl. 65, fig. 5).

Shell shaped like a lantern, with two sharp strictures. Length of the three joints = 1 : 2 : 12, breadth = 1 : 4 : 7. Cephalis hemispherical, with a slender pyramidal horn of three times the length. Thorax twice as large, thorny, hemispherical, with regular, circular pores. Abdomen very long, nearly four-sided prismatic, with four superior smaller, and four inferior larger holes; the former separated by four short, divergent, perradial, the latter by four long, parallel, vertical, interradial bars. Mouth square, four-lobed. Dedicated to Wolfgang Goethe.

Dimensions.—Length of the three joints, a 0.02, b 0.04, c 0.24; breadth, a 0.03, b 0.07, c 0.1 to 0.14.

Habitat.—Central Pacific, Stations 265 to 269, depth 2550 to 2900 fathoms.

2. Cycladophora tetrapleura, n. sp.

Shell very similar to the preceding species, but differing in the following characters: Cephalis conical, with a horn of the same length. Thorax campanulate. Four ribs of the abdomen not