168 THE FOEAMINIFEEA 



uuiserial), with a porous septal face. Cretaceous. 

 Recent. 



Example. — C. dimorplia, Brady, ' Kep. " Chall." ' 

 vol. iv. 1884, p. 388, pi. xlvi. figs. 20, 21. 



This is a particularly interesting species, on 

 account of the dimorphous arrangement of its seg- 

 ments, which at first are triserial, as in Verneuilina, 

 and afterwards uniserial, as in the later segments of 

 Clavulina. It is confined to fairly shallow water in 

 tropical areas. Recent. (Plate 9, fig. F.) 



DiMOEPHOUS {T extiilarian) Foems. 



Genus Bigenerina, D'Oebigny. 



Early chambers textularian ; later chambers 

 uniserial and rectilinear. Carhoniferous to Recent. 



Example. — B.cajjreolus, D'Orbigny sp. (VidviLlina), 

 ' Ann. Sci. Nat.' vol. vh. 1826, No. 1, pi. xi. figs. 5, 6 ; 

 modele. No. 59. 



An arenaceous species distinguished by its com- 

 pressed textularian commencement. Only the last 

 chamber or so in this species is simple, and associated 

 specimens are often found with only the textularian 

 portion developed. It first made its appearance in 

 Lower Tertiary times, and it was an abundant form on 

 the London Clay sea floor, where Piccadilly now 

 stands. In recent soundings the 'Challenger' ob- 

 tained B. capreolus from 350 to 675 fathoms in the 

 N. and S. Atlantic. Goes obtained it from the 

 Caribbean Sea at 300 fathoms. Tertiary. Recent. 

 (Plate 9, fig. G.) 



