OBSERVATIONS. 



Inhabits with the preceding species. It was given 

 me by Professor William B. Rogers, to whom I have 

 dedicated the species. 



PLANORBIS ENGONATUS. 



Plate \X.—Fig. 8. 



DESCRIPTION. 



Shell yellowish; biangulated above; spire not pro- 

 foundly impressed; side of the body whirl flattened 

 and both margins carinated; aperture longitudinally 

 subovate, slightly campanulate. 



OBSERVATIONS. 



This species was found at Albany, N. Y., by Mr. 

 Alva Mason. It differs from all other species of the 

 United States in the flattened form of its lateral or 

 outer margin, &c. 



