PLATE II. 



All original figures except 14 b, 14 c, and 17 a are enlarged three diameters. 



FIGS. i6 P. nevadensis, carinate forms. 

 7-8 smooth var. 



9 operculum. 



10 Outline of Stearns' figure 



in Proc. Phila. Ac. Nat. Sci., p. 173, 

 (1883). 

 II 12 Pyrgula helvetica Mich. 



13 P. scalariformis Copy of Wolf's figure 

 in Am. Jour. Conch., Vol. V., pi. xvii., 

 fig- 3- 



14-16 P. mississippiensis. 

 17-19 P. spinosus. 



All figures except 10 and 13 are drawn from specimens in the authors' cabinets. 



