«ONCHIFERA. 448 



valve oblique or spiral, with, two hinge teeth, the anterioi 



3 A ..r^^m c 



Fig. 246. Caprinella triangularis, Desm. U. Greensand, Rochelle, f . 

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

 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 gi'oove ; 

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

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



supported by a plate which divides the umbonal cavity length- 

 wise. 

 In C. triangularis the umbonal cavity of the spiral yalve i£ 



Fig. 247. Straight valve. Fig. 248. Spiral valve. 



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



I, position of ligamental inflection ; t, teeth ; c, cartilage pits ; v, nmbonai cavity. 



Fig. 248 is from a weathered specimen, which has lost the outer lay»r. Tee tubes %/ 



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



partitioned off at regular intervals (Fig. 246, A) ; the length of 

 the water chambers is sometimes 3^ inches, and of the body- 



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

 men, and is turned towards the spire of the large valve, (Pal. Franc, pi. 542, 5g. 

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

 umbo of the smaller valve is turned awai/ with a sigmoid flexure. (Q. J. Geol. Sou, 

 VI. yl. IS.) 



