PUPILLIDAE 



97 



Gastrocopta arniifera abbreviata (Stcrki). Fig. D. The 

 abbreviata shell, about one-eighth inch (3.5-4.0 mm.) in height, 

 may be known by the short, pointed form of the columellar 

 lamella and by a distinct basal fold which is entirely absent or 

 only feebly developed in armifera armifera. The variety abbrevi- 

 ata is rare in Illinois and has been found in only two counties, 

 Winnebago and Jackson. 



The variations in this species are not racial in the sense 

 characteristic of variations in some other snails, because they 

 occur anywhere withia the range of the species and are not 

 confined to any particular geographic regions. 



GASTROCOPTA CONTRACTA (Say) 



A smaller species than Gastrocopta armifera, contracta has 

 a shell that measures much less than one-eighth inch (2.5 mm.) 

 in height. It may readily be recognized by its conic form and 

 by the large lamella, a composite of the 

 parietal and angular lamellae, which near- | >^'^^. 



ly fills the aperture. The waxy white shell 

 has 5 rounded whorls with deep sutures, 

 and a conspicuous rounded ridge behind 

 the peristome. The aperture, somewhat 

 triangular in form, has 2 palatal folds, the 

 upper one small and the lower one large; 

 both are rounded and rather deeply set in 

 the aperture. It has a large, rounded and 

 deep-seated columellar lamella, in front of 

 which is a large vertical callus on the 

 inner lip. 



Fairly common over Illinois, and in 

 some localities abundant, Gastrocopta con- 

 tracta lives under a variety of conditions: 

 on river and creek floodplains where there 

 is plenty of moisture, in forests of syca- 

 more, oak and elm; on hillsides in forests 

 of oak, elm, hickory, basswood and pine ; 

 on bluffs of limestone; and even on dry 



railway embankments, although it is scarce in the last habitat. 

 It is common in isolated woodlands of oak, elm and hickory. 

 Two races of this species have been distinguished in Illinois. 



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