33 



SPECIES XX. Obliquaria decorticata (Unio 

 decorticata.} 



Shell rounded-elliptical, thick and very ven- 

 tricose ; apices prominent ; epidermis blackish, 

 nearly detached ; wrinkles separated ; nacre 

 white. Length f diam. 1 axis about i of 

 the breadth. 



I have observed this species in the museum of 

 Mr. J. D. Clifford, at Lexington, Ky. ; it inhabits 

 the Mississippi, and apparently the lower part of 

 the Ohio. In form it resembles the Lampsilis ; 

 but its lamellar tooth, instead of being flexuous, is 

 curved into an oblique and short arch. Although 

 the animal was living, almost all the epidermiswas 

 destroyed, even to the white nacre; and there 

 was perceptible at the apices, intermediary, 

 smooth, shining and olivaceous nacre. The 

 wrinkles deep and separated; a slight oblique 

 slope posteriorly ; cardinal tooth very much fur- 

 rowed ; muscular impressions very deep ; fossule 

 confluent ; breadth upwards of four inches. 



SPECIES XXI. Obliquaria interrupta (Unio 

 interrupta.) 



Shell oval-elliptical, somewhat thick, and slight- 

 ly ventricose ; epidermis reddish brown, slightly 

 4 



