374 SHELLS AND SHELL-FISH. PART II. 



Acardo Sw. Hinge almost without teeth : representing 

 the Saxacavidfe. 



Card, edentulum. Auct. 



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

 inequilateral ; the anterior side almost always gaping - 

 representing the Pholidce. 

 P, Soleniforme. Wood, transversutn. Sow. Conch. 



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



apertum. Ib. 56. f. 2. ringens. Wood, pi. 53. f.l, 2. 



FAMILY CHAMID^E. 



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. Damagcornis. 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. 



TBIDACNA Lam. Animal affixed by a byssus, which 

 passes through a large opening on the anterior side ; 

 cardinal teeth -}. 

 gigas. En. Me"th. 235. f. 1. elongata. Sow. Man. f. 57. 



* This species, by uniting Papt/ridea and Cardium, completes the circu- 

 lar succession of the sub-generic types. 



