287 



Fig, 207. Caprinella triangularis, Desm. U. Green-sand, Rochelle. f 

 A, portion of the left valve, after D'Orbigny,* the shell-wall is removed byweather- 

 ing, exposing the camerated interior. B, mould of five of the water-chambers. C, 

 mould of the body-chamber ; u, umbo of right valve ; s, of left valve ; t, dental groove : 

 a, surface from which the posterior lobe has been detached. From the originals in the 

 Brit. M. presented by S. P. Pratt, Esq. 



Caprinella, D'Orbigny. 



Type, C. triangularis, Desm. (Fig 207). Syn. Caprinula (Boissii) D'Orb. 



Shell fixed by the apex of the right valve, or free ; composed of a thick 

 layer of opeu tubes, with a thin compact superficial lamina ; cartilage inter- 

 nal, contained in several deep pits ; nmbones more or less camerated ; right 



Fig. 208. Straight valve. Fig. 209. Spiral valve. 



Transverse sections of C. Boissii, L. Chalk, Lisbon (Mr. Sharpe). 



I, position of ligamental inflection; t, teeth; c, cartilage pits; u. umbonal cavity. 



Fig. 209 is from a weathered specimen, which has lost the outer layer. The tubes of 



the shell-wall are filled with limestone containing small shells. 



* In M. D'Orbigny's figure the smaller valve has been added from another speci- 

 men, and is turned totvards the spire of the large valve, (Pal. Franc, pi. 542, fig. 

 1.) In Mr. Pratt's specimens, and those collected by M. Sharpe in Portugal, the 

 umbo of the smaller valve is turned away with a sigmoid flexure. (Geol. Journ. VI. 

 pi. 18.) 



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