54 A MANUAL OF AMERICAN LAND SHELLS. 



of same size as laterals; laterals unicuspid, bicuspid, or tricuspid, but 



with inner cusp obsolete; marginals quadrate, low, wide. 



Patula. Triodopsis. 



Microphysa. Mesodon. 



Eemitrochns. Acanthinula. 



Helicodiscus. Vallonia. 



Arion. Fruticicola. 



Ariolimax. Dorcasia. 



Prophysaon. Turrlcula. 



Binneya. Aglaja. 



HempMllia. Arionta. 



Strohila. Glyptostoma. 



Gonostoma. EuparypJia. 



Polygyra. Tachea. 



Polygyrella. Pomatia. 



8tenotrema. 



Family BULIMULIDJE. 



Animal heliciform; jaw thin with delicate distant ribs, giving the ap- 

 pearance of being formed of folds imbricated outwards, either vertical 

 or oblique, and forming at the center of the jaw an acute angle with 

 those of the opposite side. Lingual membrane of Helix, or peculiar by 

 the elongation and incurvation of the inner cusp of the lateral teeth. 

 Bulimulus. 



Family CYLINDEELLID^. 



Jaw thin, with delicate distant ribs, giving the apijearance of being 

 formed of oblique folds angular on the center ; lingual membrane nar- 

 row ; central tooth very narrow ; lateral teeth with very large, obtuse, 

 rounded, palmate cusps ; outer cusp short and small ; marginal teeth 

 quadrate, sometimes short and rudimentary, sometimes resembling on 

 a smaller scale the laterals. Shell turriculated, many whorled, last 

 whorl more or less detached ; apex often truncated. 

 Cylindrella. 

 Macroceramus. 



Family PUPIDiE. 



Jaw smooth or finely striate, lower margin with or without projec- 

 tion. Sometimes reinforced with a superior arched appendage, like 



