103 



very slightly contracted anterior to the middle; car- 

 dinal teeth compressed and oblique; within bluish- 

 white. 



SYNONYMES. 



U. sayi, Ward, Silliman's Journal, vol. xxxv., pi. 3. fig. 1. 

 U. declivis, nob., p. 45, pi. xxiii. fig. 1 of this work. 



OBSERVATIONS. 



This shell I found several years since in a small 

 stream in Greene county, Alabama, and supposed it 

 to be a perfect specimen of the declivis of Say, but 

 it differs from that species in having a narrower 

 umbo, plicated obliquely on the summit, a lighter 

 coloured and smoother epidermis, and especially in 

 wanting the "rostrum or prominent angle" of Say's 

 description of U. declivis. It inhabits the canal near 

 Savannah, where it was found by Mrs. Say; also the 

 canal at Louisville, Kentucky. The name was in- 

 advertently given as Saya?ius instead of Sayi. 



UNIO PLANILATERIS. 



Plate L VII.— Fig. 1. 



DESCRIPTION. 



Shell oblong-subovate, rather thin; disks flattened, 

 compressed anteriorly; ligament margin elevated, 

 parallel with the base, rounded at tip; umbonial slope 

 inflated and angulated; posterior slope flattened, and 

 having on its upper part short, slightly prominent 

 o 



