MAEGARITANA. 



1 



iO 



Mtja margarififa-a? Lin., Dillwyn, Wood. &c. 



Margaritana margaritifera, Lea, Tnins. Aiiier. Phil. See. vi. 1.35 ; Synops. 3(1. cd. 4.33, 



where a full synonymy may be found. 

 Margaritana arriiata, Sti.au'Sox, Shells of New England, 15 (1851). — Conrad, Synops. 



in Proc. Ac. Nat. Se. vi. 262. 



Shell transversely much elongated, ovate or kidney-shaped, thick 

 and strong ; beaks within the anterior fourth, scarcely rising above 

 the line of the hinge, very much eroded ; hinge and basal margins 

 usually curved, nearly parallel; nearly as broad before as behind the 

 hinge, and rounded ; iiKU-e pointed behind, and the tip appears as if 

 slightly truncated ; surface somewhat waved Ijy the lines of growth ; 

 epidermis close and smooth upon the disk, loosely wrinkled towards 

 the margin and posteriorly, color pitchy-black. "Within smooth, 

 bluish-white, and sometimes tinted flesh-color at the centre ; nacre 

 not extending to the margin, leaving a greenish border. Cardinal 



M. arcuata. 



teeth two in the left ^■alve, erect, strong, pyramidal, the posterior 

 one deeply grooved in front so as to form four or five denticles along 

 its edge ; one on the right valve, long, erect, a little twisted, deeply 

 grooved along its front, and with a pit each side, at base ; cavity of 

 the beaks shallow. Length, four and one half inches ; height, two 

 inches ; breadth, one and one fourth inches. 



Found in most running streams in the interior ; I have never 

 found it near the seaboard. 



It is a very common shell, and is at once known by its curved 

 form, dark color, and the want of a lateral tooth. It is the largest 

 fresh-water mussel we have. 



