TABLE OF CONTENTS. 



Page 

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Introductory Remarks 1 



I. On the American fresh-water Hydrobiin^ 12 



Genus Amnicola, GouM & Haki 12 



Genus Bvthinella, Mdq.-Taud. 17 



Genus Somatogykus, Gill ••..... 21 



Genus Flumikicola, Stm. 24 



Genus Gillia, Stm 2G 



II. On the subfamily Pomatiopsin.'e ....... 29 



Genus Pomatiopsis, (Tryon) Stm 29 



III. Systematic diagnoses of the genera of Hydrobiin^e . . .38 

 Stenothyka .......... 4i) 



Tricula 41 



LiTTORINELLA 41 



Hydrobia .43 



Bythinella 44 



Faludestrina . 45 



Pyrgula ........... 47 



Tryonia 48 



potamopyrgus . 49 



cochliopa .50 



Gillia ........... 51 



somatogyrus . .51 



Amxicola .......... 52 



LlTHOGLY'PIirS .......... 53 



Flpminicola .......... 54 



Synoptic table of the genera of HYDRODnx.E . . , , .55 

 Addenda et Corrigenda . . . . . . . . . 5^; 



Alphabetical Index 57 



( iii ) 



