MONOGRAPH Y 



OF THE 



FAMILY UNIONIDiE 



UNIO. 



GENERIC CHARACTER. 



Shell equivalved, inequilateral: cardinal teeth two 

 in each valve, irregular, generally striated, simple or 

 biparted; an elongated lamelliform tooth on the pos- 

 terior hinge margin of the right valve, and two 

 similar teeth on the corresponding margin of the left 

 valve: muscular impressions two principal ones in 

 each valve. 



OBSERVATIONS. 



Mr. Say justly remarks, that, "in North America, 

 the shells of this genus excel those of any other 

 country in magnitude, beauty, and diversity of spe- 

 cies." The rivers of Tennessee have furnished the 

 most beautiful specimens of many species common to 

 the western waters. The Ohio or Mississippi has 



