126 



SUCCINEIDAE 



present retusa magister is known in Illinois only from Rock 

 Island, Cook, Peoria and Fulton counties. 



Succinea retusa decampi Tryon. Fig. C. The shell of retusa 

 decampi, which is smaller than that of the typical retusa, meas- 

 ures about one-half inch (10-14 mm.) in height. It has 3 

 whorls, a short spire and a very large aperture. 

 Its principal distinguishing features are its smaller 

 size and its ash-colored shell, which has a margin 

 of dark brown bordering the outer lip and ascend- 

 ing the columellar region as far as the columellar 

 callus. This variety is known in Illinois only from 

 Canton, Fulton County. 



Succinea retusa illinoisensis Wolf. Fig. D. The 

 variety retusa illinoisensis, about one-half inch (12 

 mm.) in height, differs from Succinea retusa de- 

 campi in having a longer and more pointed spire 

 with 3 whorls and a shorter aperture. The body 

 whorl of retusa illinoisensis is wider in the middle 

 and peculiarly humped or angled, as is evident in 

 comparison of the figures of back views of shells 

 of these two varieties. The color of retusa illi- 

 noisensis is ashy, but the aperture edge is not 

 marked with brown as in retusa decampi. The 

 variety retusa illinoisensis is known in Illinois only 

 from Fulton and White counties. 



John Wolf, w^hose name is given as 

 the author of this Succinea, did not 

 publish a description of it. and its only 

 record in molluscan literature is in 

 A Catalogue of the Mollusca of Illinois 

 (page 114), where it is listed as a 

 species, Succinea illinoisensis. The speci- 

 mens thought to represent Wolf's species are from the type 

 locality, Canton, Fulton County, and the use in the present field- 

 book of the name Succinea retusa illinoisensis for a variety which 

 appears recognizable will remove it from the list of nude names. 

 Succinea retusa peoriensis Wolf. Fig E. The amber shell 

 of this small variety is about three-eighths inch (8-11 mm.) in 

 height. Its ovoid shell has an obtuse spire, which is proportion- 

 ally longer than that of most of the other varieties, and a more 

 nearly circular aperture. This variety appears to be rare in 



