100 



PUPILLIDAE 



GASTROCOPTA PENTODON (Say) 



Shells of the species pentodon and tappaniana are distin- 

 guished from other species of the genus Gastrocopta found in 

 Illinois in size and form. The shells measure about one-sixteenth 



" inch (1.5-2.0 mm.) in height and are 

 of an opaque white color, like par- 

 affin or spermaceti. They have a 

 simple parietal lamella and palatal 

 folds that are arranged on a white, 

 rimlike callus. 



The shell of Gastrocopta pento- 

 don has 5 rounded whorls separated 

 by distinct sutures. In shape it is 

 usually ovoid, sometimes c>'lindroid. 

 The palatal folds vary in num- 

 ber from 2 to 5, the additional folds being intermediate in size 

 between the primary upper and lower palatal folds. The shell 

 has a large rounded columellar lamella and a small basal fold. 

 It has a rather distinct crest or swelling behind the outer lip, 

 resembling that found in contracta. The parietal lamella and 

 the lower palatal fold are slightly curved. 



This species is distributed throughout Illinois, but the records 

 are widely scattered. It is found in a variety of habitats; on 

 wooded hillsides in forests of oak, cherry, iron- 

 wood and basswood, under leaves and debris 

 and also in grass in open places. It is seldom 

 found in wet places. 



Gastrocopta pentodon pentodon (Say). 

 Figs. A and B. The typical Gastrocopta pen- 

 todon is only about one-sixteenth inch (1.50- 

 1.75 mm.) in height. It has usually 5 palatal 

 folds. Variations in individual shells of the 

 typical variety are illustrated in figs. A and B. 

 Gastrocopta pentodon gracilis (Sterki). 

 Fig. C, The shell of pentodon gracilis is more 

 elongated than that of the typical pentodon, 

 and more nearly cylindrical. It has usually only 5 folds and 

 lamellae. On the outer lip, only the upper and lower palatal 

 folds are present. This variety, rare in Illinois, is at present 

 known only from Jackson, Union and Lawrence counties. 



