246 THE FOEAMINIFERA 



at the centre, often only slightly developed (especially 

 in the microspheric form). Eocene to Becent. 



Example. — C. Car2)ente7i,3YSi,dy, ' Eep. " Chall." ' 

 vol. ix. 1884, p. 752 ; also ibid. p. 751, pi. cxi. figs. 

 8 a, b (C. Guembeliaiius). . 



A great deal of interest attaches to the above 

 species, not only on account of its large dimensions 

 as a foraminifer, but also because of its conspicuous 

 occurrence in the two stages of shell development, 

 forms A and B. The megalospheric form is often 

 found in the sands of the coral islands, and bore 

 the name of G. Guembelianus. The other form, the 

 microspheric, occurs quite locally in just a few 

 places, and is the original type on which Carpenter's 

 lucid descriptions of the genus were based (see ' Phil. 

 Trans.' vol. cxlvi. 1856, p. 155, pi. xxx. figs. 1 and 3, 

 and ' Introd. Study Foram.' 1862, p. 292, pi. xix. 

 fig. 2). 



The places whence C. Carjjenteri have been 

 obtained are Borneo, the Macclesfield Bank, in the 

 China Sea, Solomon Islands, the Mauritius, and the 

 following places in the Pacific : Tonga, Fiji, Tonga- 

 tabu, and Funafuti. At the latter place Gijcloclijpeus 

 occurs in great abundance at certain depths, at about 

 50 to 60 fathoms, and the limit of its range there 

 seems to be from 30 to 200 fathoms. Becent. 

 (Plate 14, figs. D, cl, E.) 



Genus Orbitoides, D'Oebigny. 



Median plane composed of chamberlets arranged 

 in regular annuli round a distinct central chamber 



