BIVALVES. PINNA. 73 



DIVISION VI. EARED. 

 FAMILY 1. Valves rather compressed. 

 Margaritiferus Pearl. Radiatus Rayed. 



Unguis Nail., 



FAMILY 2. With one valve more convex than the other. 

 Hirundo Swallow. Morio Mulberry* 



Ala-corvi Crow's wing. 



DIVISION VII. SHELL SUBORBICULAR, LONGITUDINALLY 



STRIATED, AND MARGIN CRENULATED. 



Faba Bean. 



DIVISION VIII. SOMEWHAT TONGUE-SHAPED, APICES 

 ACUTE. 



Lingua Tongue. Camellii Camellius'. 



PINNA. FIN-SHELL, NACRE, OR SEA-WING. 



Animal a Limax : Shell bivalve, fragile, upright, gaping 



at one end, and furnished with a byssus or beard; hinge 



without teeth, the valves united into one. 



THE number of species contained in this genus is limit- 

 ed to twenty-one, and some of those are so alike, as barely 

 to admit of being called distinct. 



The usual form of the Pinnae is allied to that of the larger 

 species of muscles, being long and tapering, narrow at the 

 beaks, and gradually expanding to a considerable breadth 

 at the opposite extremity : there are some instances where 

 the form is more compressed. 



The Pinnae are by no means so entire or solid as the 

 muscles, for they are (with few exceptions) exceedingly 



