CONTENTS. 



Description of Six New Species of the Genus Unio, embracing the Anatomy of the Ovi- 

 duct of one of them, together with some Anatomical Observations on the Genus. 1 



Description of a New Genus of the Family of Naiades, including Eight Species, Four 

 of which are New ; also the Description of Eleven New Species of the Genus 

 Unio from the Rivers of the United States : with Observations on some of the 

 Characters of the Naiades. ....... 17 



Observations on the Naiades, and Descriptions of New Species of that and other 



Families. . . . . . ... . .73 



Description of a New Genus of the Family Melaniana of Lamarck. . .132 



Observations on the Naiades; and Descriptions of New Species of that and other 



Families. ......... 135 



Observations on Lamarck's Naiades. ...... 198 



Systematic Index. ......... 330 



