REPORT ON THE RADIOLARIA. 1359 ■ 



Genus 598. Rhopalocanium,^ Ehrenberg, 1847, Monatsber. d. k. preuss. Akad. d. Wiss. 



Berlin, p. 54. 



Definition. — Theopcrida (vel Tricyrtida triradiata clausa) with three Lateral 

 wings on the sides of the inversely conical abdomen, which bears no vertical terminal 

 horn on the basal apex. 



The genus Rhoiwlocanium, and the closely allied Rhopalatractus which follows, 

 differ from the preceding Theopera, their probable ancestral form, in the origin of the 

 three lateral wings from the inversely conical abdomen, the thorax bearing no wings. 

 The upper part of the wing bases, which arose formerly from the thorax, is here reduced 

 and lost. 



1. Rhopalocaniuni lasamim,n. sp. (PL 67, fig. 10). 



Shell subovate, with two distinct strictures. Length of the three joints =1:2:3, breadth = 

 1:3:4. Cephalis hemispherical, with a conical, dimpled horn of twice the length. Thorax sub- 

 conical, abdomen campanulate, both with irregular, circular pores. Three wings cyhndrical, divergent, 

 about as long as the shell, striated, with an ovate, dimpled knob ■at the distal end, their broad 

 triangular base being attached to the upper half of the abdomen. (Form rather variable.) 



Dimensions. — Length of the three joints, a 0-02, h 0-07, c 0-09 ; breadth, a 0-03, I 0-09, c 012. 



Habitat. — Central Pacific, Stations 263 to 268, depth 2650 to 3000 fathoms. 



2. Rhopalocanium ornatum, Ehrenberg. 



RJiopalocanivm or»a#!«»i Ehrenberg, 1854, Mikrogeol.,Taf. xxxvi. fig. 9; Abhandl. d. k. Akad. d. 

 "Wiss. Berlin, 1875, p. 82, Taf. xvii. fig. 8. 



Shell nearly spindle-shaped, with two distinct strictures. Length of the three joints = 1 : 3 : 6, 

 breadth = 1 : 4 : 3. Cephalis hemispherical, with a stout, cylindrical horn of twice the length, 

 bearing a dimpled cone. Thorax ovate, campanulate. Abdomen inversely conical Pores sub- 

 regular, circular, twice as large in the thorax as in the abdomen. Three wings compressed, slender, 

 divergent, slightly longer than the abdomen, bearing an ovate, dimpled cone at their distal end, 

 with the broad, triangular, striated base attached to the upper third of the abdomen. 



Dimensions. — Length of the three joints, a 0-02, h OM, c 012 ; breadth, a 0-025, b O'OS, c 0-07. 



Habitat. — Fossil in Barbados. 



3. Rhopalocanium cortinium, n. sp. 



Shell slender, ovate, nearly of the same form as, and with similar fenestration to that of Tlieo- 

 pera cortina, (PI. 67, fig. 8). It differs from the latter mainly by the absence of the three thoracic 

 ribs, characteristic of Tluopera. Length of the three joints = l : 2 : 6, breadth=l : 4 : 4. The 



' RlwpalocanixLm='Basket with clubs ; ^6-zciMii, y.xi/iou. 



