Page:Scientific results HMS Challenger vol 18 part 2.djvu/505

Rh are connected by three to four broad, horizontal rings; therefore subregular, transverse, and longitudinal rows of roundish pores are present. Mouth truncate, circular.

Dimensions.—Length of the three joints, a 0.02, b 0.07, c 0.08; breadth, a 0.02, b 0.09, c 0.07.

Habitat.—Fossil in Barbados.

Definition.— (vel Tricyrtida multiradiata aperta) with a simple corona of terminal feet around the truncate mouth. Abdomen not dilated, cylindrical or ovate. No ribs in the shell-wall.

The genus Calocyclas, and the three following closely allied genera, differ from the four preceding genera of Theophormida in the absence of radial or longitudinal ribs in the wall of the thorax and abdomen. These are completely reduced, and their terminal prolongations only remain, forming a simple or double corona around the mouth of the abdomen. They correspond therefore to Carpocanium and Anthocyrtis among the Dicyrtida. In Calocyclas the corona is simple. The mouth is not dilated, but often constricted, and the abdomen is cylindrical or ovate, not conical. The teeth of the corona are usually vertical or convergent.

Definition.—Thorax and abdomen smooth, without spines or thorns.

1. Calocyclas veneris, n. sp. (Pl. 74, fig. 5).

Shell smooth, with two distinct strictures. Length of the three joints = 1 : 2 : 2, breadth = 1 : 4 : 3. Cephalis ovate, with a large, triangular, prismatic horn of three times the length. Thorax hemispherical; abdomen cylindrical; both with regular, circular pores of equal size. Mouth truncate, with a corona of nine to twelve vertical, lamellar feet, which are as long as the abdomen, rectangular, twice as broad as their distance apart, and truncate at the end.

Dimensions.—Length of the three joints, a 0.03 to 0.04, b 0.06 to 0.08, c 0.04 to 0.06; breadth, a 0.03 to 0.04, b 0.09 to 0.11, c 0.08 to 0.1.

Habitat.—Cosmopolitan; Atlantic, Indian, Pacific, many stations; surface, and in various depths.

2. Calocyclas virginis, n. sp. (Pl. 74, fig. 4).

Shell smooth, with distinct collar, but indistinct lumbar stricture. Length of the three joints = 1 : 2 : 1, breadth = 1 : 4 : 3. Cephalis ovate, with a slender, conical horn, little shorter than the