65 



UNIO COLLINUS. 



Plate XXXVI.— Fig. 2. 



DESCRIPTION. 



Shell elliptical, rather thin, with coarse concentric 

 lines; umbonial slope rounded; posterior side slightly 

 produced, and rapidly narrowed to the extremity, 

 which is rounded; basal margin straight near the 

 middle; beaks small, slightly prominent, approximate, 

 undulated; umbones with two or three small tubercles 

 posterior to the middle; epidermis yellowish-brown, 

 obscurely rayed; within white or pale rose colour; 

 cardinal teeth oblique, robust. 



Cab. A. N. S. No. 20408. 



OBSERVATIONS. 



This species may readily be known by the small 

 tubercles on the umbones. The female, when young, 

 closely resembles U. heterodon in outline, but the usual 

 formation of the lateral teeth and the tubercles emi- 

 nently distinguish it. Inhabits North river, a branch 

 of James river, Virginia, where it was found by Mr. 

 Constant Newkirk, of Washington College, from 

 whom I received three specimens. 



