The Nautilus. 



Vol. XIII. FEBRUARY, 1900. No. 10. 



A NEW ALABAMA UNIO. 



BY LORRAINE S. FRIERSOX. 



Plate II. 

 TJnio ( -leurobema) Haglerl. 



Shell smooth, elliptical, (inequilateral. Length, 2.1. Height, 1.6. 

 Diameter, 1 (inches). (Dimensions are of a medium-sized shell; 

 they are sometimes larger.) 



Beaks low ; umbos somewhat inflated ; umbonal slope rounded. 

 Epidermis dark reddish brown, striate, rayless. Lines of growth 

 numerous and well impressed. Nacre white, rarely rose, frequently 

 spotted with green, iridescent in posterior. Teeth double in left 

 valve, single in the right. The anterior sinistral cardinal tooth is 

 wedge-shaped, and nearly squarely cut off on top. Its axis is inclined 

 at an angle of about 75° with that of its fellow, which is low, thick 

 and triangular. The laterals are stout and slightly curved. Dorsal 

 plate rather large. Muscle scars frequently confluent in front. 

 Distinct oehind and well impressed. Pallial scar well impressed in 

 front, fainter behind. 



Cavity of the beaks shallow. Cavity of the shell excavated from 

 the region of the beaks toward the posterior margin. The shell var- 

 ies in form from an almost perfect ellipse (lower figure) to a form 

 swollen in the post-basal region (upper tigs.) similar to the females of 

 Lampsilis. But there is no good reason to suppose this a sexual 

 character. 



