Page:Scientific results HMS Challenger vol 18 part 2.djvu/527

Rh inflated, nearly spherical, truncate at both poles, separated by a deep stricture from the cephalis, as well as from the conical abdomen, which is dilated gradually towards the wide mouth. Pores in the thorax subregular, circular, in the abdomen twice to four times larger, and irregular.

Dimensions.—Length of the three joints, a 0.02, b 0.06, c 0.1; breadth, a 0.02, b 0.08, c 0.1.

Habitat.—Fossil in Barbados.

13. Theoconus laterna, n. sp.

Shell conical, smooth. Length of the three joints = 1 : 2 : 4, breadth = 1 : 2 : 4. Cephalis small, ovate, with a strong, pyramidal, vertical horn three times the length. Thorax hemispherical, with subregular, circular, hexagonally-framed pores. Abdomen truncate, conical, with only fifteen to twenty very large, irregular, polygonal pores, which are separated by very thick bars of the same breadth as the horn.

Dimensions.—Length of the three joints, a 0.03, b 0.06, c 0.12; breadth, a 0.03, b 0.07, c 0.12.

Habitat.—Central Pacific, Station 266, depth 2750 fathoms.

14. Theoconus ficus, Haeckel.

Eucyrtidium ficus, Ehrenberg, 1875, Abhandl. d. k. Akad. d. Wiss. Berlin, p. 70, Taf. xi. fig. 19.

Theocorys ficus, Haeckel, 1881, Prodromus, p. 434.

Shell conical, pear-shaped, smooth. Length of the three joints = 1 : 5 : 20, breadth = 2 : 10 : 25. Cephalis very small, ovate, with a conical, straight horn three times the length. Thorax quite conical, with solid wall, without pores. Abdomen very large, nearly spherical, truncate at both poles, little constricted at the very wide mouth; its pores subregular, circular, about three times as broad as the bars. (This species is intermediate between the genera Theoconus and Theocorys.)

Dimensions.—Length of the three joints, a 0.01, b 0.05, c 0.2; breadth, a 0.02, b 0.1, c 0.25.

Habitat.—Fossil in Barbados.

Definition.— (vel Tricyrtida eradiata aperta) with conical abdomen gradually dilated towards the wide open mouth. Cephalis with two or more horns or a corona of horns.

The genus Lophoconus has the same conical shell with truncate mouth as Theoconus, and differs from it only in the armature of the cephalis, bearing either two large divergent horns (usually a larger occipital and a smaller frontal horns), or a bunch or corona of numerous divergent horns.