71 

 UNIO COMPRESSUS. 



Plate XL. — Fig. 1. 

 DESCRIPTION. 



Shell oblong or elliptical; disks flattened; anterior 

 margin regularly rounded; umbonial slope slightly 

 elevated, rounded; beaks undulated, not prominent, 

 distant from the anterior extremity; ligament margin 

 elevated, connate; posterior margin oblique, recti- 

 linear, extremity truncated and slightly projecting 

 beyond the line of the base; epidermis ochraceous, 

 with numerous unequal green rays, some of which 

 are very broad; within white, tinged with pale salmon 

 under the beaks; cardinal tooth scarcely double in 

 the right valve, very oblique, elongated, rather thick; 

 in the left valve widely trifid, compressed, posterior 

 lobe rather behind the apex. 



SYNONYMES. 



U. compressus, Deshayes. 



Symphynota compressa, Lea. Trans. Amer. Phil. Soc, (new 



series,) vol. iii. p. 450, pi. xii. fig. 22. 

 Cab. A. N. S. No. 1098. 



OBSERVATIONS. 



This species can at once be distinguished from all 

 others by the peculiarity of its hinge. It inhabits 

 the Ohio, Scioto, and Wabash rivers; also Oak Orch- 

 ard creek, in the State of New York, and Norman's 

 Kill, near Albany. The figure is from a specimen 

 which I found in a mill pond at the village of Adams, 



