Page:Scientific results HMS Challenger vol 18 part 2.djvu/843

Rh 1. Conchasma radiolites, n. sp. (Pl. 123, fig. 5).

Shell nearly spherical, somewhat compressed on both sides; the dorsal valve smaller, flatter and shorter than the ventral valve. In the half sagittal perimeter of the shell twenty to twenty-two pores, in the half frontal perimeter twelve to fourteen, in the half equator eighteen to twenty. All pores nearly of the same size, circular, hexagonally framed, scarcely as broad as the bars. The two horns of the hinge are four-sided pyramidal, of different sizes; the ventral horn (of the larger valve) two to three times as long as the dorsal horn (of the smaller valve); the latter twice as long as a pore.

Dimensions.—Length of the shell 0.16, height 0.15, breadth 0.14.

Habitat.—Antarctic Ocean, Station 154, depth 1800 fathoms.

2. Conchasma sphærulites, n. sp. (Pl. 123, fig. 6).

Shell nearly spherical, somewhat compressed on both sides, the frontal diameter therefore somewhat shorter than the two others. Both valves nearly of the same size, hemispherical, their borders smooth, twice as broad as the largest pores. In the half sagittal perimeter of the shell twenty-eight to thirty pores, in the half frontal perimeter twenty to twenty-two, in the half equator twenty-four to twenty-six. Size of the pores increasing from the borders towards the top of the valves. One series of very small pores along the frontal free margin of each valve. Pores roundish-polygonal, three to four times as broad as the bars. The two horns of the hinge are of equal size, four-sided pyramidal, and twice as long as the larger pores.

Dimensions.—Length of the shell 0.18, height 0.18, breadth 0.16.

Habitat.—Antarctic Ocean, Station 152, depth 1260 fathoms.

3. Conchasma hippurites, n. sp.

Shell nearly spherical, scarcely compressed. The frontal diameter equal to the two others. Both valves equal. In the half sagittal perimeter of the shell thirty-two to thirty-four pores, in the half frontal perimeter twenty-four to twenty-six, in the half equator twenty-six to twenty-eight. All pores of nearly equal size, circular, polygonally framed, twice as broad as the bars. The two horns of the hinge are large, three-sided pyramidal, the ventral horn twice as long as the dorsal, and four to six times as long as one pore.

Dimensions.—Length of the shell 0.22, height 0.21, breadth 0.2.

Habitat.—Antarctic Ocean, Station 157, depth 1950 fathoms.

Definition.— with the lateral margins of the two valves dentate, the teeth of both catch one into another.