374 SHELLS AND SHELL-FISH. PART II. 



Acardo Sw. Hinge almost without teeth : representing 

 the Saxacavidce. 



Card, edentuluin. Auct. 



Papyridea Sw. Shell heart-shaped, or transversely oval; 

 inequilateral ; the anterior side almost always gaping ' 

 representing the Pholidcu. 



P. Soleniforme. Wood, transversum. Sow. Conch, 



Conch, pi. 56. f. 3. f. 4.* 



apertum. lb. 56. f. 2. ringens. Wood, pi. 53. f. 1, 2. 



FA3IILY CHAMID^. 



Animal marine ; shell often attached, irregular, not per- 

 laceous, with or without short siphons ; lateral teeth on 

 the posterior side of the shell only ; cardinal teeth variable, 



Hippopus Lam. Cuneate ; both valves closed ; bosses 

 nearly central; cardinal teeth small; lateral teeth 

 long, posterior. 

 C. maculatus. Sow. Gen. f. 1. En, Meth. 236. f. 2. 



Pleurorynchus Phillips. Anterior end abruptly trun- 

 cate, as in Hemicardium : the hinge margin elongated 

 into earlike processes. Fossil only, 

 elongatum. Sow. Min. Con. avicularis. Sow. Gen. f. 2. 



Chama Linn. Shell irregular, attached by the lower 

 valve ; a single lengthened tooth in one valve, and a 

 corresponding groove in the other. 

 C. Damscornis. Sow. Gen, f. 1. arcinella. Sow. Gen. f. 2. 



Isocardia Lam. Shell heart shaped, regular, ventricose ; 

 bosses remote, receding, turbinate ; cardinal teeth 

 lamellar. 



I. cor. En. Meth. 232. f. 1. 



Tridacna Lam. Animal affixed by a byssus, which 

 passes through a large opening on the anterior side ; 

 cardinal teeth -j-. 

 gigas. En. M^th. 235. f. 1. elongata. Sow. Man. f. 57, 



* This species, by uniting Papyridea and Cardium, completes the circu- 

 ]ar succession of the sub-generic types. 



