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.
Genus 616. Theosyringium, Haeckel,[[233]] 1881, Prodromus, p. 434.
Definition.—Theocorida (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).