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.—Cephalis 0.04 diameter; thorax 0.12 long, 0.1 broad,

Habitat.—Central Pacific, Station 265, depth 2900 fathoms.

3. Tetrahedrina quadricornis, Haeckel.

Lithochytris triangula, Bury, 1862, Polycystins of Barbados, pl. xix. figs. 4, 5, 6.

Shell pear-shaped, papillate, with slight collar stricture. Length of the two joints = 1 : 5, breadth = 1 : 5. Cephalis subspherical, with a stout conical horn twice the length. Thorax with irregular, roundish, lobulated pores, with three conical, stout, divergent feet at the base, of the same size and form as the cephalic horn.

Dimensions.—Cephalis 0.02 diameter; thorax 0.1 long, 0.1 broad.

Habitat.—Fossil in Barbados.

Genus 556. Sethochytris,[^[173]] Haeckel, 1881, Prodromus, p. 433.

Definition.—Sethoperida (vel Dicyrtida triradiata clausa) with three terminal latticed feet or hollow, fenestrated, divergent, basal apophyses of the thorax. Cephalis with a horn.

The genus Sethochytris differs from the preceding Tetrahedrina in the fenestration of the three basal feet, which form direct protrusions or evaginations of the three basal corners of the pyramidal shell. It may be derived from Sethopera by centrifugal growth of the basal corners.