ZONITID^E. 1 



* 



Subgenus STRTATURA, Morse, 18G4. 



Shell small, striate, thin, translucent, without teeth in the 

 aperture. 



Jaw almost smooth, with a median furrow and notch ; central 

 tooth of the radnla very large. United States. 



Distinguished chiefly by the jaw and dentition. 



Section PSEUDOHYALINA, Morse, 1864. 



Shell minute, subdiscoidal, slightly convex above, unicolored, 

 closel}* striate-ribbed, umbilicus moderate. N. America. 



Chanoiiiphalii*, Strebel, 1880, is a synonym. 



Section PYCNOGYRA, Strebel, 1880. 



Shell many-whorled, depressed conical above, whorls narrow, 

 ribbed-striate, translucent ; umbilicus rather large, bordered by 

 an obtuse angle. Mexico. 



Subgenus JAM us. I, owe-. 1852. 



Shell unibi Heated, depressed orbicular, costulately striate 

 above, rather smooth below ; whorl 7-8^, closely revolving, the 

 last convex at the base; aperture lunar, peristome simple, thin, 

 with a callous rin^ within. Madeira. 



O 



Jaw and radula typical. 



Genus SELKN1TKS, Fischer, 1879. 



Shell depressed orbicular, widely perspectively umbilicated, 

 strongly striate above, last whorl obliquely depressed above, 

 depression becoming more marked at the aperture; extremities 

 of the peristome approaching. 



Animal having the jaw of Zonitida?, but the dentition of the 

 Testacellida 1 . United States. 



On account of the jaw and dentition, Dr. Fischer has made 

 this group the type of a family Selenitidre, interposed between 

 Testaceilidae (having similar teeth, but no jaw), and ZonitidaB 

 (having similar jaw, but different teeth). 



Section HAPLOTREMA, Ancey, 1881. 

 Shell much smaller, peristome sharp. 



Section MORCHIA, Albers, 1860. 



Shell darker colored, striatulate. West Indies. 



