156 AMERICAN JOURNAL 



HydrobiiNuE. Shell elongated, perforate, smooth. Opercu- 

 lum corneous. European and American. Liitorinella, 

 Sydrohia^ Bythinella, Paludestrina* 



Amnicolin^. Shell turbinate ; whorls very convex, umbili- 

 cate ; aperture round ; peristome continuous. Ameri- 

 can. Amnicola. 



POMATIOPSIN^. Foot with lateral sinuses. Shell elongate ; 

 margin of aperture slightly expanded. Terrestrial or 

 amphibious. American. Pomatiopsis. 



CoCHLiOPiN^. Shell heliciniform, heavy; aperture oblique ; 

 umbilicus large, with an angulated margin. American. 

 Gochliopa.\ 



L1THOGLYPHIN.E. Shell subglobular ; spire short ; aperture 

 large, half round ; peristome not continuous; imperforate 

 or slightly perforate. European and American. GilUa, 

 Somatogyrus, Lithoglyphiis, Fluminicola. 



For comparison, we copy the arrangement of Hydrohiinse 

 adopted by Dr. Stimpson. 



* The animals of Tricula, Pyrgula, and Tryonia are undescribed, and I 

 will not venture to assign their place, believing that the two last named 

 belong decidedly to another family. Does not Potamopyrgus, St., belong 

 to the same group ? 



t I almost doubt the pertinence of Cochliopa to this family, although Dr. 

 Stimpson's description of the Soft Parts seems to place it here. 



