TO MAJOR JOHN LE CONTE. 



My Deak Friend: 



Will you permit me in this way to acknowledge my obligations to 

 your great kindness and liberality, in furnishing me, during so many years, with nume- 

 rous new species of our fluviatile molluscs? The pains you have always taken in 

 bringing to light new forms, may readily be understood by looking through this and 

 my previous volumes on this interesting subject. I feel grateful for the untiring assi- 

 duity you have given to promote my objects, and therefore it is with peculiar pleasure 

 that I present you with this volume. 



Truly and 

 , Faithfully yours, 



ISAAC LEA. 



