19 



4 diam. 15 mill, or more; umbilicus quite narrow, or 



almost closed. 5 



— diam. ab. 13, alt. 5 mill., color pale horn; umbili- 



cus rather narrow (introduced from Europe.) 



cellaria, Mull. 



5 diam. 20; alt. 6 mill.; color brownish or smoky horn. 



subplana, Binn. 



— diam, 16; alt. 6 mill.; color yellowish horn 



inornata, Say. 



6 diam. 4 to 5 mill.; whorls in the spire and suture flat; 



surface shining; color light horn to brownish. 7 



— diam. 3 mill, or less. 9 



7 umbilicus none or very narrow, whorls 4^, surface 



with irregular impressed striae; color light horn, or 

 almost colorless. indentata, Say 



— umbilicus rather wide. 8 



8 whorls rather wide and rounded, and so the aper- 



ture; striation fine and rather regular; deep to 

 brownish horn colored. (Eu.) radiatula, Aid. 



— whorls rather depressed, narrower, and so the aper- 



ture; striation fine and irregular; sh. dusky or 

 brownish horn colored, or almost colorless. 



wheatleyi, Bid. 



9 whorls 3, rather rapidl}' increasing; surface not with 



membraneous ribs. 10 



— whorls ab. 4, slowly increasing. 1 1 



10 diam. 3, alt. 1.3 mill.; surface dull, but rather 



smooth; color light steel gray; umbilicus moderate. 



ferrea, Mse. 



— diam. 1.5, alt. 0.6; surface with regular, oblique, 



microscopic stria?, color light greenish yellow; 

 umbilicus wide. milium, Mse. 



11 with rather regular membraneous ribs sometimes al- 



most obsolete; umbilicus wide, color light grayish 



or yellowish horn. exigua, Stimpson. 



