28 



UNIO NEBULOSUS. 



Plate 111.— Fig. 7. 



DESCRIPTION. 



Shell elono-ated, narrow-elliptical, thin, convex, 

 olivaceous, clouded with dark brown, and with green 

 interrupted rays; posterior side produced, rather 

 pointed, and truncated at the end; hinge margin 

 slightly arched; ligament slope compressed; beaks not 

 l)rominent, undulated; posterior margin oblique, and 

 rectihnear I'rom the end of the lateral tooth to the 

 angle of the truncated extremity; cardinal teeth very 

 oblique and compressed; within bluish Avhite and ici- 

 descent, or purple. 



OBSERVATIONS. 



This species is alhed to U. iris, Lea, but is readily 

 distinguished by its narrowed posterior end and an- 

 gular margin. This shell is thin and fragile, very 

 iridescent, and generally bluish; but I have one 

 specimen with the nacre of a deep purple colour 

 and highly polished. I found this species only in the 

 mountainous region of Alabama, in the Black War- 

 rior river. 



UNIO COR. 



Plate III.— M^. 3. 

 DESCRIPTION. 



Shell obliquely cordate; thick, with concentric fur- 



