98 KANSAS UNIVERSITY QUARTERLY. 



shell ver}' thick, almost uniformly so; convexity greatest along mid- 

 dorsal line. 



Measurements: 



Length 45 mm 



Width 38 " 



Height 15 " 



Locality: Saline river, Ellis county, Kansas. 



Remarks. — This is the largest species of the genus. The characteristic left 

 valve is entirely different from the other species as will be seen from the descrip- 

 tions. Unfortunately no left valves of this species have been collected. 



