268 MARINE SHELLS 



2. A. *pexata. Shell covered with a hairy epi- 

 dermis, transversely subovate, with from thirty-two 

 to thirty-six ribs, placed nearer to each other than 

 the length of their own diameters ; umbones moder- 

 ate ; apices approximate, placed far backward, very 

 near the posterior termination of the hinge ; posterior 

 edge rounded, destitute of an angle ; anterior edge 

 rounded, with an angle at the termination of the 

 hinge ; inferior edge regularly rounded. 



Length one inch and seven-tenths. 



Breadth two inches and three-tenths. 



Inhabits the coast of the United States. 



Cabinet of the Academy and Philadelphia Mu- 

 seum. 



A common species, distinguished by the name of 

 the bloody clam. It is covered with a hairy epider- 

 mis, and when violently opened, an effusion of a red 

 sanies proceeds from the animal. In the young shell, 

 an angle is perceptible on the posterior edge, at the 

 termination of the hinge margin, but this disappears 

 with age. 



3. A. *incongrua. Shell somewhat rhomboidal, 

 with from twenty-six to twenty-eight ribs, placed 

 nearer to each other than the length of their own 

 diameters, and crossed by elevated, obtuse, equal, and 

 equidistant lines, which are altogether wanting on 

 ten rays of the disk of the left valve : apices opposite 

 to the middle of the hinge, distant from each other, 

 with a lanceolate space between them, of which the 

 breadth is about one-third of its length $ extremities 



