UNIO FLAVUS. 



Plate XLI. — Fig. 2. 



DESCRIPTION. 



Shell sub-triangular, moderately thick; disks flat- 

 tened on the posterior side; anterior margin obtusely 

 rounded; ligament margin oblique, rectilinear; poste- 

 rior margin wide, straight, nearly direct; extremity 

 obtuse; basal margin straight from the posterior ex- 

 tremity to beyond the middle; umbonial slope cari- 

 nated; umbo rather prominent; beaks flattened, with 

 a few obtuse oblique undulations; within salmon 

 colour; cardinal and lateral teeth large and very pro- 

 minent. 



SYNONYMES. 



U. flava, Ef. Ann. gen. des Sc, vol. v. p. 59. Poulsoirs 



trans., p. 38. 

 U. rueiginosus, Lea. Trans. Amer. Phil. Soc., new series, vol. 



iii. p. 41, pi. viii. fig. 10. 

 Cab. A.N. S.Xo. 1126. 



OBSERVATIONS. 



This shell is so distinctly described and even figured 

 by Rafinesque, that no honest inquirer can refuse 

 him credit for the species. He remarks that he found 

 "it only in the small rivers falling into the Kentucky, 

 Salt or Green rivers." This peculiarity of habitat 

 is remarkable, and I Avas unable to find a specimen 

 in either the Alabama, Tombeckbe, or Black Warrior 

 rivers, although several were found in a small mill 

 stream in Greene county, Alabama. Rafinesque re- 



