REPORT ON THE RADIOLARIA. 1295 



nearly as long as the shell. Thorax slenderly conical, rough, with straight outlines, and irregular, 

 roundish pores, gradually increasing in size towards the mouth. 



Dimensions. Cephalis O'Ol diameter, thorax 0'09 long, 0'03 broad. 



Habitat. Indian Ocean (Zanzibar), depth 2200 fathoms (Pullen). 



18. Sethoconus gracilis, Haeckel. 



Ewyrtidium gracile, Ehrenberg, 1875, Abhandl. d. k. Akad. d. Wiss. Berlin, p. 70, Taf. xi. 

 fig. 15. 



Cephalis small, subspherical, with few scarce pores, and a stout, pyramidal horn, of the same 

 length. Thorax slenderly conical, three to four times as long as broad, with straight outlines, and 

 very small and numerous circular pores of equal size. 



Dimensions. Cephalis 0'015 diameter, thorax 012 long, 0'04 broad. 



Habitat. Fossil in Barbados. 



19. Sethoconus bimarginatus, n. sp. (PL 54, fig. 12). 



Coniutella bimarginata, Haeckel, 1879, Atlas, loc. dt. 



Cephalis very small, subspherical, hyaline, without pores, with a rudimentary, conical horn of the 

 same length. Thorax slenderly conical, three times as long as broad, with undulated, little convex 

 outlines, and irregular, roundish, double-contoured pores, arranged in nine longitudinal series, 

 markedly increasing in size towards the mouth. 



Dimensions. Cephalis O'Ol diameter, thorax 016 long, 0'05 broad. 



Habitat. South Pacific, Station 300, depth 1375 fathoms. 



20. Sethoconus daihratus, Haeckel. 



Cornutella clathrata, Ehrenberg, 1854, Mikrogeol., Taf. xxii. fig. 39a, b, c. 



Cephalis very small, subspherical, hyaline, without pores, with a rudimentary horn of half the 

 length. Thorax slenderly conical, three to four times as long as broad, smooth, with curved axis and 

 small, regular, circular pores, nearly equal in size. This common species differs from all others of 

 the genus by the curvation of the axis of the shell, which is more or less crescentic, or curved like a 

 cowherd's horn ; it may, therefore, represent a peculiar genus, Sethodrepanum. 



Dimensions. Cephalis 0'003 to 0'006 diameter, thorax 0'08 to 016 long, 0'03 to 0'05 broad. 



Habitat. Cosmopolitan ; Atlantic, Pacific, many stations ; fossil in Barbados and Sicily. 



Subgenus 3. Phlebarachnium, Haeckel (et Cladarachnium, Haeckel), 1881, 



Prodromus, p. 430. 



Definition. Cephalis small, with very small pores, and internal collar septum. 

 Thorax spiny or thorny. 



