17 



14 diam. 6 mill, or more 15. Polygyra. 



— diam. 3 mill, or less. 15 



— diam. 20 mill.; umbilicus very wide; whorls 5 well 



rounded; peristome slightly everted with a thin lip; 

 sh. nearly colorless; S. Selenites. 



15 no internal lam. 14. Vallonia. 



— with internal lam. 16. Strobilops. 



16 whorls about 3, rapidly increasing, the last and the 



aperture very wide; peristome-margin straight 

 and thin. 21. Succinea. 



— whorls more than three, moderately increasing 17 



17 aperture scarcely higher than wide; sh. cylindrical, 



narrowly umbilicated, with slightly conic, rather 

 obtuse apex; peristome-margin thin and straight 

 without any lam. or teeth; alt. 2 to 2.5; diam. i mill. 



9. Sphyradium. 



— aperture higher than wide, or with lam., or margin 



with a strong lip. 18 



18 very small, needle-like, apex pointed; glassy color- 



less; peristome. with a strong lip with 2 or 3 small 

 teeth; on the columella of the penultimate whorl 

 a large tortuous lam.; alt. about 1.8 mill. 



22. Carychium 



— not so 19 



19 columella truncated below; sh. narrowly oblong, 



deep horn colored, transparent; surface shining; 

 peristome-margin straight, slightly thickened; 

 alt. 6, diam. 2.5 mill, 20. Ferussacia. 



— columella not truncated; sh. different, 20 



20 sh. turriculate, peristome with a strong flat lip and 



usually a small angular nodule; no lam.; color deep 

 horn to brownish; alt. 5 to 6, diam. 2.5 mill. 



17. Buliminus. 

 - — sh. ovate, or ovate conic, to oblong or cylindrical; 

 (ours) with from three to ten lam. and folds in the 

 aperture. 21 



