REPORT ON THE RADIOLARIA. 1397 



Genus 611. Tlieocalyptra,^ Haeckel, 1881, Prodromus, p. 434. 



Definition. — Theocorida (vel Tricyrtida eradiata aperta) with diseoidal or flatly 

 expanded abdomen. Cephalis with a single apical horn, or with two divergent horns. 



The genus TJieocalyptra, and the follouang closely allied genus Cecnjphalium, 

 differ from all the other Theocorida in the flattened form of the cap-shaped or nearly 

 diseoidal shell. The abdomen specially is quite flat, often horizontally expanded, and 

 like the mai'ginal brim of a flat hat. They may be derived from the Dicyrtida Setho- 

 cephaliis by the development of an abdomen, or from Corocalyptra by loss of the 

 collar wings. The network is usually very delicate, as in the latter. The cephalis of 

 Theocalyptra bears one or two horns. 



1. Theocalyptra veneris, n. sp. 



Shell flatly campanulate, very delicate and fragile, very similar to Eucephryphalus agtiesce 

 (PI. 59, fig. 3), but without collar spines. Length of the three joints = 1 : 4 : 2, breadth = 1 : 7 : 9. 

 Cephalis hemispherical, with a single bristle-shaped horn of twice the length. Thorax sub- 

 conical, separated from the flatter abdomen by a deep stricture, with thin bars, and large, subregular, 

 hexagonal meshes, increasing in size towards the smooth mouth-edge. 



Dimensions. — Length of the three joints, a 0'02, I 0"07, c 004 ; breadth, a 0-025, b 0'15, c O'L 

 Habitat. — Cosmopolitan ; Atlantic, Indian Pacific, many stations, surface. 



2. TJieocalyptra orci, Haeckel. 



Halkaliiptra orci, Ehrenberg, 1872, Abhandl. d. k. Akad. d. Wiss. Berlin, p. 293, Taf. x. 

 figs. 9, 10. 



Shell flatly campanulate, very similar to the preceding species in general form and fenestration, 

 but flatter and smaller, with different proportions. Length of the three joints = 7 : 2 : 1, breadth = 

 1:6:8. Cephalis hemispherical, very small, with two divergent, bristle-shaped horns of the same 

 length. Abdomen nearly horizontally expanded. 



Dimensions. — Length of the three joints, a 0-015, b 0-04, c O'Ol ; breadth, a 0-02, b 012, c 0-16. 



Habitat. — Indian Ocean, Zanzibar, depth 2200 fathoms (PuUen). 



3. TJieocalyptra discoides, Haeckel. 



Cydadoplwra discoides, Ehrenberg, 1875, Abhandl. d. k. Akad. d. Wiss. Berlin, p. 68, Taf. 

 xviii. fig. 4. 



SheU flatly campanulate, similar to the two preceding species, but not so delicate, with thicker 

 bars, and roundish, not hexagonaL meshes. Length of the three joints =1:2:2, breadth = 3:6:9. 



1 Theocalyptra = 'Dvrm(^ veil; li6i, xa^v^rrj*. 



