PART II. 



ATBACHT A OSTRACIDjE. 



387 



umbones lateral or sublateral ; byssus protruded near 

 the umbones. 



Margarita Leach. (1817.) Shell more or less rounded ; 

 auricles small ; umbones sub-lateral ; the hinge mar- 

 gin straight, but not lengthened ; teeth small, tuber- 

 culated, nearly obsolete, (fig. 126. e.) 

 crocata. Zool. 111. ii. pi. 55. 



Amcula Lam. Shell obliquely oval ; the hinge margin 

 very much lengthened, and forming unequal auricles ; 

 teeth tuberculous, nearly or quite obsolete, (fig. 121. 



M,*) 



A. heteroptera. Sow. Gen. f. 1. aculeata. Ib. f. 2. 



PINNA. Shell equi valve, wedge-shaped or triangular ; 

 umbones terminal ; the other extremity widely gaping ; 

 hinge margin straight ; teeth none ; anterior margin 

 slightly gaping.* (fig. 126. /, ff.) 

 P. serrata. Sow. Gen. 



FAMILY 4. OSTRACTD^l. Oysters. 



Animal sedentary, generally affixed by their under valve ; 

 shell foliaceous, rarely pearly, (fig. 1 29-) 



PECTEN Linn. Shell regular, depressed, nearly orbicular, 

 auriculated ; umbones central ; ligament small ; in- 

 ternal hinge margin short ; teeth straight. 



* This genus, by coming close to Mytilzts completes the circle of this 

 family. 



C C 2 



