60 



UNIO ELLIPSIFORMIS. 



Plate XXXIV. Fig. 1. 



DESCRIPTION. 



Shell elliptical, slightly ventricose, produced pos- 

 teriorly, moderately thick; disks slightly contracted 

 anteriorly; umbonial slope rounded; beaks slightly 

 prominent, approximate, simple; basal margin dilated 

 posteriorly to the middle; within bluish; cardinal teeth 

 thick, direct. 



OBSERVATIONS. 



This species I have seen only in the cabinet of Mr. 

 John Phillips, who received it from Michigan. It is 

 very similar in outline to U. lienosus, but the short, 

 thick, direct teeth, simple beaks, and bluish nacre, 

 form a very distinctive character. 



UNIO LIENOSUS. 



Plate XXXIV. Fig. 2. 



DESCRIPTION. 



Shell elliptical, inflated, slightly furrowed or con- 

 tracted from beak to base; substance of the shell 

 thickened towards the base; posterior dorsal and 

 posterior basal margin rounded, extremity subangu- 

 lated; beaks pointed, approximate, slightly prominent, 



