116 



of this shell is in no respect dissimilar from forms of Unio parvua found in gravelly 

 river bottoms in more northern regions, and it is very doubtful if it can maintain 

 a place in the system as a separate or distinct species. The species belongs to the 

 parvus group without a question, though the specimens under examination are 

 eroded and do not exhibit the characteristic coarse undulations on the umbones. 

 In all other particulars my shells are typical. 



To complete the history of these small and difficult forms the original diag- 

 noses of Lea, except one, and Conrad have been tabulated and thrown into synop- 

 tical form as follows: 



