OUTLINE OF THE CLASSIFICATION OF THE LAND AND 

 FRESH' WATER MOLLUSCA OF THE UNITED STATES 



Class GASTROPODA 



MoUusks with a more or less distinct head and a broad, flat foot; usually 

 with a spirally wound shell 

 Subclass PULMONATA 



No true operculum; no gills; cavity between body and mantle serv 

 ing as lung; hermaphroditic 

 Order BASOMMATOPHORA 



Usually aquatic (one family terrestrial) ; with one pair of con' 

 tractile tentacles, with a pair of eyes at their bases 

 Family CARYCHIIDAE (ELLOBIIDAE) 



Small terrestrial or amphibious snails; shell usually with elon- 

 gate, folded, and often toothed aperture 

 Common genera — Melampus 

 Carychium 

 Family LYMNAEIDAE 



Aquatic; tentacles flattened; shell thin, usually acutely pointed, 

 and with a large and often flaring aperture; lip thin and simple 

 Common genus — Lymnaea 

 Family PLANORBIDAE 



Aquatic; tentacles thread'like or cylindrical; shell usually dis' 

 coidal, sinistral or apparently dextral 



Common genera — Helisoma Drepanotrema 



Armigera PJanorhula 



Gyraulus Carinifex 



Promenetus Parapholyx 



Menetus 

 Family ANCYLIDAE 



Small; aquatic; tentacles triangular; shell cap-like, scarcely or 

 not spiral 



Common genera - — Ferrissia Rhodacmea 



Lanx Amphigyra 



Gundlachia l\[eoplanorhis 



Family PHYSIDAE 



Aquatic; tentacles thread-like; shell sinistral, with large lower 

 whorl 



Common genera — Physa 

 Aplexa 

 Costatella 



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