OP THE MOLLUSC A OF IOWA. 81 



Uhio mulliplicalus Lea. Mississippi river : rare. Re- 

 placed in the interior streams of the state by U. plicatus, 

 and U. undulalus. 



Unio orbiculatus Hildreth. Mississippi river : not com- 

 mon. 



Unioparvus Lea. Generally distributed in the streams 

 throughout the state, but not abundant. 



Unio phaseolus Hildreth. This species has been re- 

 ported from the state but no specimens have been 

 personally examined. 



Unio plicatus LeSueur. Abundant at Iowa City, and in 

 eastern Iowa generally. In the Des Moines and other 

 streams of the central portion of the state it is replaced by 

 U. undulatus. 



Unio pressus Lea. A few specimens taken in the Des 

 Moines river at Des Moines : very rare. 



Unio pustulatus Lea. Rare in the Mississippi and 

 streams of northeastern Iowa ; common in the Des Moines 

 river at Bonaparte, Van Buren county. 



Unio pustulosus Lea. Des Moines and Raccoon rivers : 

 common. In these streams the variety described as U. 

 schoolcraftii is quite abundant. 



Unio pyramidatus Lea. Southeastern Iowa : rare. 



Unio reclus Lamarck. Common in the streams of 

 nearly every portion of the state. Specimens having 

 a beautiful salmon colored nacre have been collected in the 

 Rock and Des Moines rivers. 



Unio rubiginosus Lea. Abundant in the Rock, Des- 

 Moines and Raccoon rivers ; rare in many localities. 



Unio schoolcraftii Lea. Abundant in the Raccoon, Des 

 Moines and Iowa rivers. Gradates into U. pustulosus, with 

 which it is undoubtedly synonymous. 



Unio securis Lea. Common in the Mississippi and its 

 tributaries of eastern Iowa. 



