Hershler, Robert. <br/><br/>
Systematics of the North and Central American aquatic snail genus Tr yonia (Rissooidea : Hydrobiidae) /    
Robert Hershler. 
 - Washington, D.C. :   Smithsonian Institution Press,   2001. 
 - 53 p. :    ill., maps ;    28 cm. 
 - Smithsonian contributions to zoology ;   no. 612. .
<br/><br/>Includes bibliography : p. 51-53. 
<br/><br/><label>Subjects--Topical Terms: </label><br/>Tryonia --------Classification.