Report on the Radiolaria Collected by H.M.S. Challenger During the Years 1873-1876, Second Part: Subclass Osculosa; Index / Report on the Scientific Results of the Voyage of H.M.S. Challenger During the Years 1873-76, Vol. XVIII

by Ernst Haeckel

Dimensions.—Length of the three joints, a 0.02, b 0.04, c 0.02; breadth, a 0.02, b 0.15, c 0.2.

Habitat.—Central Pacific, Station 274, surface.

Genus 613. Theoconus,[^[230]] n. gen.

Definition.—Theocorida (vel Tricyrtida eradiata aperta) with conical abdomen, gradually dilated towards the wide open mouth. Cephalis with a single horn.

The genus Theoconus, and the following closely allied Lophoconus, differ from the other Theocorida in the conical or campanulate form of the shell; the abdomen is a truncated cone, gradually dilated towards the terminal mouth. The latter is usually truncated, widely open, sometimes with a slightly constricted peristome. The cephalis of Theoconus bears a single apical horn.

Subgenus 1. Theocorax, Haeckel.

Definition.—Pores of the thorax and of the abdomen of nearly equal size and similar form.

1. Theoconus zancleus, Haeckel.

Eucyrtidium zancleum, J. Müller, 1858, Abhandl. d. k. Akad. d. Wiss. Berlin, p. 41, Taf. vi. figs. 1-3.

Eucyrtidium zancleum, Haeckel, 1862, Monogr. d. Radiol., p. 321.