ER OST 6G bo 2 ee 
OF THE 
FLUVIATILE MOLLUSCA 
OF 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. 
