12 ZONITID^E. 



Section PATULOPSIS, Strebel, 1880. 



Shell Patula-like, periphery angulated, upper surface finely 

 ribbed-striate, umbilicus open, perspective. Left cervical lobe 

 of the mantle divergently bipartite. Mexico. 



Section ^EGOPINA, Kobelt, 1879. Europe. 



Includes the larger European species and is scarcely distinct 

 from Omphalina. Retinella, Shuttl., is a synonym. 



Section MESOMPHIX, Rafinesque, 1819. 



Shell umbilicate or perforate, conical or conical-depressed, thin, 

 plicately striated, brownish horn-color, usually lighter colored 

 below ; whorls close ; aperture lunar ovate, lip sharp, subreflexed 

 on the columella. United State*. 



Barely distinguished from Omphalina by its closer whorls, 

 plicate strife, and more conical form. 



Subgenus GASTRODONTA, Albers, 1850. 



Shell subperforate or narrowly umbilicated, orbicularly 

 depressed, light horn-color, sometimes glassy, with more 

 or less numerous wrinkle-like striae ; whorls, 5-7 ; aperture 

 lunate, its interior with lamellar denticles, not reaching the 

 acute margin. United States. 



Section GASTRODONTA (typical >. 



Denticles within the outer and basal walls of the aperture, 

 occurring at rest-periods of the growth and persistent. 



Section YENTRIDENS, Binney and Bland, 1869. 

 Aperture with revolving series of pliciform teeth within the 

 base only. 



Section HELICODISCUS, Morse, 1864. 



Minute, planorboid, with spiral stria 1 ; aperture lamellarly 

 toothed within the outer lip. 



'( Section ODONTOSAGDA, Martens, 1860. 



Shell whitish, depressed, thin, umbilicated ; whorls 6, the last 

 with convex base ; aperture lamellarly toothed. Haiti. 



? Section PROSERPINULA, Albers, 1860. 



Discoidal, hyaline, transparent, covered perforate ; whorls 4^. 

 planulate, the last with shining callus around the umbilical 

 ivgion ; aperture with a spiral lamella attaining tho margin. 



Jamaica. 



