292 Natural History Bulletin. 



Sub-Kingdom MOLLUSCA. 

 Class GASTEROPODA. 



Family rissoid^. 

 Bithynella obtusa Lea. 



Family valvatid^. 

 Valvata tricarinata Say. 



Family succiniDyE. 



SUCCINEA OVALIS Gould. 



SucciNEA AVARA Say. 



Family limn^id^. 



Li:MNyEA STAGNALIS L. 

 LlMN^A PALUSTRIS Muell. 



LiMN^A DEsiDiosA Say. 



LlMN^A CAPERATA Say. 



Physa gyrina Say. 



Planorbis trivolvis var. macrostomus Whiteaves. 



Planorbis bicarinatus Say. 



Planorbis albus Muell. 



Planorbis parvus Sa}-. 



Segmentina armigera Say. 



Class LAMELLIBRANCHIATA. 



Family cyrenid^. 

 Sph^rium sulcatum Lam. 

 Sph^rium striatinum Lam. 



1 Identified by Mr. B. Shimek, of the State University of Iowa. 



