Page:Scientific results HMS Challenger vol 18 part 2.djvu/533

Rh roundish pores beyond the lumbar stricture, and two to four succeeding transverse rows of irregular, roundish, smaller pores. Mouth widely open, truncated.

Dimensions.—Length of the three joints, a 0.02, b 0.05, c 0.06; breadth, a 0.03, b 0.08, c 0.07.

Habitat.—Fossil in Barbados.

Definition.— (vel Tricyrtida eradiata aperta) with cylindrical abdomen, which is much narrower than the inflated thorax, and forms a slender, narrow tube, with truncated mouth. Cephalis with a single horn.

The genus Theosyringium differs from the closely allied Theocyrtis, its ancestral form, in the wide inflated thorax, which is much broader than the narrow tubular abdomen. The mouth of the latter is small and truncate.

1. Theosyringium tibia, n. sp. (Pl. 68, fig. 4).

Shell rough, very slender, with two distinct strictures. Length of the three joints = 1 : 3 : 4, breadth = 1 : 2 : 1. Cephalis ovate, with a conical horn of the same length. Thorax ellipsoidal. Abdomen cylindrical, as long as the two former joints together. Pores subregular, circular.

Dimensions.—Length of the three joints, a 0.03, b 0.09, c 0.12; breadth, a 0.03, b 0.06, c 0.02.

Habitat.—Central Pacific, Station 263, depth 2650 fathoms.

2. Theosyringium pipetta, n. sp. (Pl. 68, fig. 5).

Shell rough, inflated, with two sharp strictures. Length of the three joints = 2 : 7 : 9, breadth = 2 : 7 : 2. Cephalis conical, with a slender horn of half the length. Thorax subglobose. Abdomen cylindrical, as long as the two former joints together. Pores subregular, circular.

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

Habitat.—Central Pacific, Station 268, depth 2900 fathoms.

3. Theosyringium siphonium, n. sp.

Shell rough, inflated, with two deep strictures. Length of the three joints = 1 : 3 : 3, breadth = 1 : 2 : 1. Cephalis subspherical, with a stout pyramidal horn of twice the length. Thorax broad ovate. Abdomen slender, inversely conical, as long as the thorax, and one-third as broad as the base. Pores subregular, circular, hexagonally framed, (Similar to Eusyringium conosiphon, Pl. 78, fig. 10, but only with two strictures and three joints.)

Dimensions.—Length of the three joints, a 0.03, b 0.1, c 0.1; breadth, a 0.03, b 0.07, c 0.025.

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