974 



FRESH-WATER BIOLOGY 



AURICULIDAE 



FIG. I. Carychium exiguum Say. 



SlPHONARIIDAE 



29 27 17 15 13 11 9 1 



f^ 



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FlG. II. Siphonaria alternata Say. 



GADINIIDAE 



FIG. III. Gadinia reticulata Say. 



LYMNAEIDAE 



FIG. IV. Lymnaea stagnate L. 



PLANORBIDAE 



8 H 



FIG. V. Planorbis trivolvis Say. 



