REPORT ON THE RADIOLARIA. 1239 



3. Tetrahedrina quadricornis, HaeckeL 



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



Shell pear-shaped, papillate, with sKght collar strictura Length of the two joiiits=l: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. 



Dimensioiis. — Cephalis 0'02 diameter ; thorax O'l long, O'l broad. 



Habitat. — Fossil in Barbados. 



Genus 556. Sethochytris,^ Haeckel, 1881, Prodromus^ p. 433. 



Definition. — S etlioperida (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. 



1. Sethochytris triconiscus, n. sp. (PI. 57, fig. 13). 



Shell rough, with deep collar stricture. Length of the two Joints = 1:8, breadth = 1:3. 

 Cephalis spherical, with an oblique pyramidal horn of the same length. Thorax campanulate, 

 conical ; its three basal corners prolonged into three divergent, slender, hoUow, fenestrated cones, 

 twice as long as the thorax, and ending in a stout pyramidal spine. 



Dimensions. — Cephalis 0'04 diameter, thorax 012 diameter, length of the feet 0"2. 



Habitat. — Central Pacific, Station 268, depth 2900 fathoms. 



2. Sethochytris barhadensis, Haeckel. 



Lithochytris barhadensis, Ehrenberg, 1875, Abhandl. d. k. Akad. d. Wiss. Berlin, p. 160,- 

 Taf. V. fig. 2. 



Shell smooth, with slight coUar stricture. Length of the two joints = 1:6, breadth = 1:4. 

 Cephalis ovate, witli a conical horn of half the length. Thorax conical ; its base prolonged into 

 three divergent, hollow, fenestrated cones, half as long as the thorax. Pores small, subregular, 

 circular. 



Dimeiisions.-^C e]ihalis 0-025 diameter, thorax 01 diameter, length of the feet 0'05. 



Habitat — Fossil in Barbados. 



' Sethochytris = Sieve-'pot; oijiu, x"'''?';- 



