Brownish; about I/4"; Ariz., Texas and N. M. 

 Thysanophora horni (Gabb) 



245. About Vs"; whorls four; shell pale; generally distributed 



Hawaiia minuscula (Binney) 

 About i/j"; whorls about four and one-half 246. 



246. Shell closely striate; shell pale; northeastern and north-central states 



Zonitoides limatulus (Binney) 

 Shell scarcely striate; shell horn colored; generally distributed 

 Zomtoides arboreus (Say) Amber Leaf Snail 



247. Shell almost discoidal; body whorl with fine revolving ridges which are 



beaded, rather than smooth as in H. parallelus (Choice 232); about 



Vs"; s. c. 



Clappiella saludensis (Morrison) 

 Not so 248. 



248. Aperture constricted by a thickening within the lip and by a parietal 



callus or tooth; shell almost discoidal, with six to eight whorls 249. 

 Aperture not so 250. 



249. Spire concave; with a parietal callus; V4"; California 



Ammonitella yatesi (Cooper) Yates's Snail 

 Spire flat to convex; with a tooth on the parietal wall; V2''' northwestern 

 U.S. 



Polygyrella polygyrella (Bid. and Cooper) 



250. Body whorl regularly expanded 251. 

 Body whorl flaring toward the aperture to become about twice as wide 



as the whorl next to it 256. 



251. With six or seven whorls 252. 

 With about five whorls 253. 



252. Body whorl with radial rows of small teeth within the base and usually 



visible through the shell; lip thin; about 3/16"; central states 

 Paravitrea significans (Bland) 

 With a lamella or thick callus at base of aperture; about V2''; Tenn. to 

 Ala. 



Ventridens lasmodon (Phillips) 



253. Body whorl toothed within, near the aperture; about Vs"; Tenn. to 



Ala. 254. 



Not so 255. 



254. Aperture toothed within, on columellar and parietal regions; Tenn. 



Pilshryna aurea Baker 

 Body whorl wth a series of four double-pointed teeth within last half; 

 Tenn. to Ala. 



Clappiella aldrichiana (Clapp) 



255. Spire flattened; usually with slightly over five whorls; about 3/16"; west' 



ern states 



Microphysula ingersolli (Bland) 

 Spire somewhat elevated; usually with slightly under five whorls; about 

 I/4"; generally distributed 



Zonitoides arboreus (Say) Amber Leaf Snail 



142 



