46 



POLYGYRIDAE 



POLYGYRA FRAUDULENTA (Pilsbry) 



The shell of Polygyra fraudulenta greatly resembles and Is 

 often mistaken for that of Polygyra tridentata. Shells of both 

 species are about one-half inch (13 mm.) in diameter, both are 



umbilicated and both have 3 

 denticulations in the aperture. 

 But the spire of fraudulenta is 

 higher, the umbilicus is larger 

 and deeper, the body whorl is 

 more rounded and the aperture 

 is much higher. The notch be- 

 tween the two peristome den- 

 ticles is also much deeper and narrower than that in tridentata. 

 The shells of fraudulenta vary much in color and may be 

 described as ashy, horn, light brown or reddish brown. The 

 pure white expansion of the aperture and the white tubercle on 

 the parietal wall stand out in marked contrast against the 

 darker shell. 



The animal of Polygyra fraudulenta, resembling that of 

 Polygyra tridentata, is dark blue or slate in color. 



In Illinois, this species is now found only in the tributary 

 valleys of the Wabash, Ohio and Mississippi rivers, where it 

 is very abundant in well-wooded areas in forest debris, under 

 logs and about limestone boulders. Because it seems to prefer 

 the small ravines and valleys, fraudulenta is not usually found 

 with tridentata, which more frequently inhabits the cliffs of the 

 larger streams. 



Polygyra fraudulenta was first recognized by Dr. Henry A. 

 Pilsbry, of the Academy of Natural Sciences of Philadelphia, 

 in 1894. It had been mistaken by Dr. William G. Binney for 

 Polygyra fallax (Say), which is an eastern species, while 

 fraudulenta is a snail of the Middle West, although its dis- 

 tribution eastward is as far as Maryland. 



Be Thine own home, and in thyselt dwell; 



Inn anywhere; continuance maketh hell. 



And seeing the snail, which everywhere doth roam, 



Carrying his own house still, still is at home, 



Follow (for he is easy-paced) this snail, 



Be thine own palace, or the world's thy jail. 



— John Donne, Verse to Sir Henry If'otton 



