INTRODUCTION. vil 



Lea, Conrad and others, in American works, and not 

 included in Lamarck's enumeration. 



This compilation is intended for those only who 

 study recent shells, and not for those who would study 

 that department of the animal kingdom which ordina- 

 rily bears shells. All reference to the inhabiting ani- 

 mal is therefore omitted, and those genera which bear 

 no shell, or are only found in a fossil state, are merely 

 defined in their proper places, and the names of 

 fossil species are not mentioned. It is supposed that 

 those who would pursue the study to these particu- 

 lars, will have access to the original work. 



A. A. G. 



