110 



from the same locality with the first described, which 

 present the very remarkable character of spines, one 

 on each valve, proceeding in an erect position from 

 near the middle of the disk. In one old specimen 

 there is no trace of these spines, but in the only two 

 middle aged specimens I received the spines are as 

 well developed as represented in the figure. A spi- 

 nous Unio, no doubt the same species, is said to 

 occur abundantly near Columbia in South Carolina. 

 This is a smaller species, less pointed posteriorly, 

 and otherwise distinct from the U. spinosus of Lea. 



UNIO TRABALIS. 



Plate LX.— Fig. 2. 



DESCRIPTION. 



Shell oblong-ovate, ventricose, thick anteriorly; 

 anterior side short, margin obtusely rounded; poste- 

 rior side cuneiform, produced, obtusely rounded at 

 the extremity, which is narrow; hinge margin decli- 

 ning; posterior margin slightly contracted just above 

 the extremity of the valve; umbonial slope rounded; 

 posterior slope flattened or concave, in old shells 

 furrowed; beaks eroded and rather prominent; basal 

 margin arched; epidermis smooth and polished, dark 

 olive-brown tinted with green, and with dark green 

 unequal rays, not very distinct; within dull white or 

 slightly salmon-coloured anteriorly; bluish and very 

 iridescent posteriorly; cardinal tooth in the right 

 valve very thick and direct, in the left valve the car- 



