28 
UNI O NEBULOSUS. 
Plate III.— Fig. 7. 
DESCRIPTION. 
Shell elongated, 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 
prominent, undulated; posterior margin oblique, and 
rectilinear from the end of the lateral tooth to the 
angle of the truncated extremity; cardinal teeth very 
oblique and compressed; within bluish white and iri- 
descent, or purple. 
OBSERVATIONS. 
This species is allied 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 Biack War- 
rior river. 
UNIO COR. 
Plate III. — Fig. 3. 
DESCRIPTION. 
Shell obliquely cordate; thick, with concentric fur- 
