im: o IN" o (3 i^^^ip h: 



OF THE 



FLUVIATILE MOLLUSCA 



OP THE 



UNITED STATES. 



PREFACE. 



The following pages are devoted to the 

 illustration and description of the fresh-water 

 univalve mollusks inhabiting the United 

 States, together with notices of some of the 

 extra-limital species ; and the work forms part 

 of a series, which is intended to comprise a 

 complete history of the mollusca of our coun- 

 try. 



One volume of this series (that on the ter- 

 restrial shells*) has already been published, 

 and the present volumes describe all the fluvia- 

 tile families with the exception of the Strepo- 



*A Monograph of the Terrestrial Mollusca of the United 

 States. With Illustrations of all the Species, By Geo.W. 

 Tryon, Jr. 8vo, 204 pp. 18 plates. Philadelphia, 1866-7. 



