168. Lip thickened and well reflected; aperture toothed or toothless; shell 



unhanded in most but not all species 169. 



Lip slightly reflected below; rarely with one tooth on the parietal wall; 



usually, hut not always, with one or more revolving bands of color 189. 



169. Minute (Vs") shells; widely umbilicated; striate to ribbed; aperture 



toothless; generally distributed 170. 



Not so 171. 



170. Shell definitely ribbed 



Vallonia costata (Miiller) 

 Shell striate 



Vallonia pulchella (Miiller) 



171. Mostly in Ari2;ona and New Mexico; shells plain colored; moderate sized 



shells (Many species, of which this is representative) 



Ashmunella ashmuni (Dall) White-lipped Desert Snail 



Generally distributed, except in the two states mentioned; usually plain 



colored, but with bands of color in a few species; about V2" to 1" 



(Many species, formerly of the genus Polygyra, of which a few are 



given here) Large-mouthed Wood Snails 172. 



172. Umbilicus closed 173. 

 Umbilicus open 180. 



173. With a long, oblique tooth on the parietal wall, and usually with one or 



two teeth on the lip 174, 



Toothless or with one small tooth on the parietal wall 177. 



174. Umbilicus indented, sometimes slightly exposed; body whorl smoothly 



rounded; about Vz"' central and southeastern states 

 Mesodon (Infiectarius) inflectus (Say) 

 Umbilicus concealed; body whorl usually somewhat angulate or keeled 



175. 



175. Lip usually with only one small tooth near the base of the aperture; Vz''' 



to y/'; east-central states 



Mesodon (Patera) appressus (Say) 

 Lip usually with two teeth 176. 



176. Body whorl keeled; no hairs on epidermis; about 1"; central states 



Triodopsis (Xolotrema) ohstricta (Say) 

 Body whorl angulate; epidermis with fine hairs; about %" to T'; eastern 

 and east-central states 



Triodopsis (Xolotrema) notata (Deshayes) 

 (Polygyra denotata (Ferussac) ) 

 (Polygyra palUata (Say) ) 



177. Shell usually with many fine dark lines; umbilicus indented; about %" to 



1''; central states 



Triodopsis (Heohelix) multilineata (Say) Many-lined Wood 

 Snail 

 Color not in fine revolving lines; umbilicus concealed 178. 



134 



