CONCHIFERA. 449 
_ 
valve oblique or spiral, with two hinge teeth, the anterior 
Fig. 246. Caprinella triangularis, Desm. U. Greensand, Rochelle, 2. 
A, portion of the left valve, after D’Orbigny,* the shell-wall is removed by weathe: 
ing, exposing the camerated interior. B, mould of five of the water-chambers. C, 
mould of the body-chamber; uw, 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 tha 
Brit. Mus., presented by S. P. Pratt, Esq. 
supported by a plate which divides the umbonal cavity iength- 
wise. 
In C. triangularis the umbonal cavity of the spiral valve is 
Fig. 247. Straight valve. Fig. 248. Spiral valve. 
Transverse sections of C. Boissiz, L, Chalk, Lisbon (Mr. Sharpe), 
1, position of ligamental inflection; t, teeth; c, cartilage pits ; w, umbonal cavity. 
Fig. 248 is from a weathered specimen, which has lost the onter layer. Tre mbes of 
the shell-wall are filled with limestone contaming 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’Orbigny’s figure the smaller valve has been added from another gpaci- 
men, and is turned towards the spire of the large valve, (Pal. Franc. pl. 542, fig. 
1). In Mr, Fratt’s specimens, and those collected by Mr. Sharpe in Portugal. the 
umbo of the smaller valve is turned away with a sigmoid flexure. (Q. J. Geol. Sou, 
VI. pl. 18.) 
