PUPILLIDAE 103 



Genus VERTIGO Draparnaud 



The small pupoids of the genus Vertigo differ from most 

 snails of the genus Gastrocopta in having brown shells. Of the 

 Illinois Gastrocopta snails only Gastrocopta procera has a brown 

 or cinnamon-colored shell. 



The outer lip of the usual J'ertigo shell has an indentation 

 in the middle, the shell is usually more globose in form than that 

 of the gastrocoptas and the parietal and angular lamellae are 

 more often separated to form distinct denticles. 



The animal lacks the tentacles of other pupoids. The eye 

 peduncles are long and pointed. The body of the animal is short, 

 blunt before and tapering behind. 



Several species of Vertigo are found in Illinois. Special 

 search should be carried on by Illinois conchologists for members 

 of this genus, of which species other than those listed in this 

 handbook may be found living in the state. Vertigo gouldii 

 Binney has been reported by Hinkley from Rockford, Winne- 

 bago County, and by Marsh from Will County, but these 

 reports have not been verified. No specimens have recently been 

 seen from Illinois which could be referred to this species. How- 

 ever, it has been authentically reported by Daniels from Indiana 

 and may possibly be found in the northern part of Illinois. 



Key to Species 



1. Palatal folds very long and extending far back into aperture 



milium^ p. 107 



Palatal folds tubercular and placed near edge of peristome, 

 p. 104 2 



2. Aperture with 2 denticles on parietal wall and 2 columellar 



denticles, p. 104 3 



Aperture with only 1 denticle on parietal wall and 1 col- 

 umellar denticle, p. 106 4 



3. Shell cylindroid; whorls 6} 2 morsei, p. 104 



Shell ovoid or ventricose; whorls 5 ovata, p. 105 



4. Aperture with but 1 palatal denticle and with no basal 



denticle tridentata^ p. 106 



Aperture with 2 palatal denticles and a conspicuous basal 

 denticle, p. 105 at bottom 5 



5. Shell cylindroid; whorls 5; palatal denticles on a callus bor- 



dering aperture elatior, p. 106 



Shell ventricose or ovoid; whorls 4; palatal folds or denticles 

 not on a callus ventricosa, p. 105 



