8 AMNICOLA DECISA. 



concave, in contact with the shell posteriorly, 

 and nearly so throughout its length. 



COLOR pale green, and slightly translucent 

 when the black foreign matter is removed. 



GEOGRAPHICAL DISTRIBUTION. Inhabits small 

 streams connected with the Susquehanna, and 

 has been observed in the Schuylkill by Dr. 

 Griffith. 



' OBSERVATIONS. 



Allied to Paludina similis, Mich., of Europe. 

 A greater portion of the labium lies close to 

 the shell in this species than in any other here 

 described, except A. nicliniana, and A. tenuipes, 

 which are slender species. At first view it 

 might be taken for a minute Paludina decisa, 

 and I have named it accordingly. In my cor- 

 respondence I have hitherto called this species 

 limosa. 



