PUPILLIDAE 



109 



Genus COLUMELLA Westerlund 



As in the genus Pupoides, the aperture of the shell in 

 Columella is devoid of folds or lamellae. The shape of the 

 Columella shell suggests an immature Gastrocopta. The lip or 

 peristome in Columella is never reflected, as in Pupoides, but 

 always thin and sharp. Only one species of this genus is recorded 

 from Illinois. 



COLUMELLA EDENTULA (Draparnaud) 



One of the two species of Illinois Pupillidae without folds 

 or lamellae within the aperture, Columella edentula has a brown 

 shell one-sixteenth inch (1.5-2.5 mm.) in length. The 5 to 6 

 whorls are rounded, the aperture is almost 

 circular, the peristome is sharp and thin and 

 the parietal wall is turned over in such a 

 way as partly to conceal the small umbilicus. 

 This shell differs from that of Pupoides 

 marginatus in its smaller size, blunter spire 

 whorls, more nearly cylindrical shape and 

 sharply edged outer lip. 



Apparently Columella edentula, a north- 

 ern species, is not common in Illinois. It has 

 been recorded from only three counties, 

 McHenry, Fulton and Washington, in the 

 northern, central and southern parts of the 

 state. The Illinois habitats are under leaves in damp woods of 

 floodplain areas. Unlike most of the other small snails of Illinois, 

 this species does not occur in colonies; usually only a single 

 specimen is found in a place. 



Columella edentula has been known under several names. 

 It is listed in other manuals as Pupa simplex, Pupa edentula, 

 Vertigo simplex and Sphyradium edentulum. 



Although the species Columella edentula is now rare in 

 Illinois, a related species. Columella alticola (Ingersoll), was 

 widely distributed throughout Illinois during the Pleistocene 

 geological period. Columella alticola is abundant in fossil 

 deposits known as loess, and its distribution extended as far 

 east as central Illinois. It is found living at the present time in 

 the higher regions of Colorado and other western states. 



