CONCHIFEKA. 449 



yalve oblique or spiral, with two hinge teeth, the anterior 

 3 A M C 



Fig. 246. Caprinella triangularis, Desrn. U. Greensand, EocheUe, |. 

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

 ing, exposing the camerated interior. B, mould of fiv_' 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. Mas., 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 valve is 



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 ; w, umbonal cavity. 



Fig. 243 is from a -weathered specimen, -which has lost the outer layer. The tubes of 



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



partitioned oS 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 speci- 

 men, and is tiu-ned towards the spire of the large valve, (Pal. Franc, pi. 542, fig. 

 1). I:i Mr. iiatt's specimens, and those collected by INIr. Shai-pe in Portugal, the 

 umbo of the smaller valve is turned away with a sigmoid tiexm-e. (Q. J. Geol. Soc. 

 VI. i>l. 18.) 



