174 Mr. Barnes on the Genera Unio and Alasmodonta. 
extremity pointed, posterior rounded ; epidermis greenish 
brown ; surface striated, glabrous ; cardinal teeth slender ; 
lateral tooth long and thin; naker bluish-white varied with 
wax-yellow, and sometimes tinged with violet, and irides- 
cent; cavity of the beaks, scarcely any. . 
Remarx.—This cannot as M. Lamarck supposed be his 
Unio Nasuta, for it has no sinuses on the basal margin, 1s. 
not “ crooked” nor “ obliquely attenuated.” 
27. Unio Gracii1s.—Shell ovately triangular, very 
thin and fragile, hinge margin elevated ; valves 
connate ; ligament concealed. : 
Unio Alatus. Mr. Say. 
Inhabits the Wisconsan. Mr. Schoolcraft. 
nd the Lakes. Mr. Say. 
Cabinet of the Lyceum. 
My Collection. 
Diam. 1°0—1-2 Length 2°2—2°5 Breadth 3:1—4'1. 
Beaks depressed, and placed far back; ligament between 
the valves, and covered; anterior lunule distinct and obso- 
letely ribbed ; hinge margin elevated into a large wing; 
pce sea-green, wrinkled and striated transversely ; 
obscurely radiate and glabrous; cardinal teeth very small, 
scarcely projecting; lateral teeth very thin and finely stria- 
ted ; channel just sufficient to admit the point of the thumb 
nail; naker bluish-white tinged with violet, and beautifully 
iridescent. 
Remarxs.—This shell differs from Unio Alatus in being 
much thinner, broader in proportion, lighter color both in- 
side and outside, produced and somewhat pointed behind ; 
anterior slope ina straight line with the alated projection. 
It differs entirely in the shape and proportion of the teeth. 
28. Unio Pinyin Fig. 18. eS 
Shell oblong-ovate, small, convex, sides round- 
ed; beaks slightly elevated, inside pearly white, 
iridescent. | 
