Shell pear-shaped, with two distinct strictures. Length of the three joints = 2 : 3 : 16, breadth = 3 : 6 : 16. Cephalis hemispherical, with few small pores. From its apex arises vertically a very long three-sided prismatic horn with denticulate edges, three to four times as long as the shell. An inner thin prolongation of the horn descends vertically nearly to the mouth, and bears on its basal end three verticils of branched spines, each verticil with three divergent forked spines (fig. 1a). Pores regular, circular, in the subspherical abdomen three times as large as in the hemispherical thorax. The constricted mouth is scarcely broader than the thorax.
Dimensions.—Length of the three joints, a 0.02, b 0.03, c 0.16; breadth a 0.03, b 0.06, c 0.16.
Habitat.—Central Pacific, Station 271, depth 2425 fathoms.
Genus 621. Lophocorys,[[238]] Haeckel, 1881, Prodromus, p. 434.
Definition.—Theocorida (vel Tricyrtida eradiata aperta), with ovate abdomen, broader than the constricted mouth. Cephalis with two divergent horns, or with a bunch of horns.
The genus Lophocorys differs from its ancestral form, Theocorys, only in the armature of the cephalis, bearing either two divergent horns, or a corona of several radial horns. In two species there are four horns on the apex, a larger vertical (occipital) horn being surrounded by three smaller, upwards divergent horns.
1. Lophocorys astrocephala, n. sp. (Pl. [69], fig. 9).
Shell smooth, inversely ovate, with deep collar and slight lumbar stricture. Length of the three joints = 3 : 7 : 6, breadth = 4 : 11 : 10. Cephalis subspherical, stellate, densely covered with numerous (ten to twenty or more) divergent, large, slenderly conical horns, the longest of which reach the length of the shell. Thorax campanulate, with small, regular, circular pores. Abdomen tapering towards the constricted mouth, in the upper half with the same pores, in the lower half with smaller, scarce pores, or nearly hyaline.
Dimensions.—Length of the three joints, a 0.03, b 0.07, c 0.06; breadth, a 0.04, b 0.11, c 0.1.
Habitat.—Central Pacific, Station 266, depth 2750 fathoms.