ZONITIDAE 73 



Genus PARAVITREA Pilsbry 



In Illinois occur two species of the genus Paravitrea which 

 might at first sight be taken for variations of one of the Retinella 

 snails, especially electrina, wheatleyi or rhoadsi. Three distinct 

 differences separate the Paravitrea snails from any of the 

 Retinella group. The shells of Paravitrea have 6 whorls {Reti- 

 nella, 4) ; the whorls are very tightly coiled (in Retinella, loosely 

 coiled) ; and the small, round and deep umbilicus is placed exactly 

 in the center of the base of the shell {Retinella has the umbilicus 

 somewhat off center because the last whorl is expanded). 



The genus Paravitrea is a group new to Illinois collectors, 

 neither of the two species represented appearing in A Catalogue 

 of the Mollusca of Illinois. The genus includes 18 species and 

 races, mostly southern in distribution. Central Illinois appears 

 to be the northern extension for the genus except for one peculiar 

 form, Paravitrea multidentata, named by William G. Binney, 

 which extends its range as far north as the states of Maine and 

 Michigan. 



Key to Species 



Aperture obliquely ovate significans, p. 74 



Aperture horizontally ovate capsella, p. 73 



PARAVITREA CAPSELLA (Gould) 



The pellucid amber shell of the snail Paravitrea capsella 

 is less than one-fourth inch (5 mm.) in diameter. The height 

 is one-half the diameter. The 6 whorls are very tightly coiled, 

 the spire is flattened and the surface is marked with distinct, 

 spaced, radiating and impressed lines. The aperture is regu- 

 larly lunate, and the deep umbilicus is placed in the center of 

 the round base. 



The animal is blackish in color. 



This zonitoid, formerly known as Vitrea capsella, in Illinois 

 is confined largely to the southern half of the state, its northern- 

 most record being Vermilion County. It may be found under 

 loose bark, on the underside of fallen branches and, rarely, 

 under leaves in woodlands of oak, hickory, elm and pine. As 

 a rule only a few specimens of Paravitrea capsella are found in 

 one locality. 



