224 AMERICAN JOURNAL 



Sub-order Limnophila. 



Amphibious and fluviatile species. Head furnished with 

 two tentacuke, with eyes at their bases. 



A few of these shells are considered terrestrial, because they 

 inhabit land within reach of the tides. 



§ Shell oval-ohhng or conoidal, mouth dentate within. 

 Not umhilicate. 



Family AuriculidvE. 



The American are all sea-shore species, except one minute 

 shell {Carychium exiguum) which extends far inland, upon 

 river margins and in damp places. 



Section B.— PHANEROPNEUMONA (Operculata). 



Shell operculate. Head furnished with two tentaculse, with 

 eyes sessile at their bases. Respiratory orifice without a valve. 



Sub-order Ectopathalma. 



Eyes lateral, at the external bases of the tentacles. Oper- 

 culum spiral or concentric. 



§ Shell orlicular or turhiiiate, whorls convex, lip con- 

 tinuous, reflected^ umbilicus open or indented. 



Family Cyclophorid^. 



A few species inhabit the Gulf States. 



§§ Shell depressed, conical, ivhorls hut little convex, lip 

 not continuous, reflected, umbilicus covered by a heavy 

 deposit of callus. 



Family Helicinidje. 



Tropical. Several species in the Gulf States, and one found 

 as far north as Indiana. None in California. 



Sub-order Opisopthalma. 



Eyes placed posterior to the bases of the tentacles. Oper- 

 culum sub-spiral. 



§ Shell cylindrical, apex truncate. 



Family TRUNCATELLIDiE. 



Inhabiting sea-shores of Florida and California. 



