974 



FRESH-WATER BIOLOGY 



30 29 



AUEICULIDAE 



t^t^t^n 



nn^ 



Fig. I. Carychium exiguum Say. 



SiPHONARIIDAE 



Fig. n. Sipkonaria alternata Say. 



Gadinhdae 



Fig. III. Gadinia reticulata Say. 



Lymnaeidae 





Fig. IV. Lymnaea stagnalis L. 



Planorbidae 



C 1 ~ 8 M 



tio. V. PlanorUs Irivolm Say. 



