Dimensions.—Cephalis 0.015 long, 0.04 broad; thorax 0.15 long, 0.12 broad.
Habitat.—North Pacific, Station 253, depth 3125 fathoms.
Genus 571. Clistophæna,[[188]] Haeckel, 1881, Prodromus, p. 433.
Definition.—Sethophænida (vel Dicyrtida multiradiata clausa) with terminal apophyses. Cephalis with a horn.
The genus Clistophæna agrees with the preceding Sethophæna in the mouth of the thorax being closed by a lattice-plate. But the appendages of the thorax are terminal feet, not lateral wings; their number is commonly six or nine, rarely more. Clistophæna may be derived either from Tetrahedrina by interpolation of secondary feet between the three primary, or from Sethamphora by development of a basal lattice-plate closing the mouth.
1. Clistophæna rüstiana, n. sp. (Pl. [57], fig. 6).
Shell rough, with distinct collar stricture. Length of the two joints = 3 : 10, breadth = 4 : 11. Cephalis hemispherical, with small, circular pores and a stout oblique horn three times the length, which is three-sided prismatic, and at the top denticulate. Thorax subconical, inflate, with regular, circular, quincuncial pores, increasing in size towards the base. Margin of the flat base, with six divergent, stout feet of the same prismatic form as the cephalic horn, with denticulate distal ends, about as long as the thorax. This elegant species is dedicated to Dr. Rüst of Freiburg, the discoverer of numerous fossil Radiolaria in the Liassic and Jurassic formations.
Dimensions.—Cephalis 0.03 long, 0.04 broad; thorax 0.1 long, 0.11 broad.
Habitat.—Central Pacific, Station 265, depth 2900 fathoms.
2. Clistophæna hexolena, n. sp.