Page:Scientific results HMS Challenger vol 18 part 2.djvu/557

Rh 4. Tricolocapsa decandollei, n. sp. (Pl. 66, fig. 4).

Shell subovate, with two sharp strictures. Length of the three joints = 2 : 2 : 2, breadth = 3 : 4 : 3.5. Cephalis campanulate. Thorax broader, ring-shaped. Abdomen inversely hemispherical. All three joints of the same length, thick-walled, with the same regular and peculiar reticulation, the small circular pores being surrounded by square, elevated frames.

Dimensions.—Length of the three joints, a 0.07, b 0.07, c 0.07; breadth, a 0.10, b 0.14, c 0.12.

Habitat.—Western Tropical Pacific, Station 225, depth 4475 fathoms.

Definition.—Thorax much smaller than the abdomen.

5. Tricolocapsa brownii, n. sp.

Shell ovate, very thick-walled, with two indistinct strictures. Length of the three joints = 2 : 4 : 7, breadth = 3 : 7 : 10. Cephalis flat, hemispherical. Thorax truncate, conical. Abdomen inflated, inversely hemispherical. Pores regular, circular, of the same breadth as the bars, hexagonally-framed, twice as large in the abdomen as in the thorax. Basal pole rounded.

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

Habitat.—Fossil in Barbados.

6. Tricolocapsa schleidenii, n. sp. (Pl. 66, fig. 2).

Shell subconical, with two deep strictures. Length of the three joints = 2 : 3 : 6, breadth = 3 : 5 : 6. Cephalis subspherical. Pores subregular, circular, arranged in transverse girdles, three in the broad thorax, six in the subglobular abdomen. Basal pole rounded.

Dimensions.—Length of the three joints, a 0.02, b 0.03, c 0.06; breadth, a 0.03, b 0.05, c 0.06.

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

Definition.— (vel Tricyrtida eradiata clausa) with an apical horn, and a lattice-plate between thorax and abdomen.

The genus Phrenocodon differs from the two preceding genera in the remarkable circumstance, that the basal lattice-plate closes not the terminal mouth itself, but the