M 



Brvant Walker 



Subgenus PLANORBULA lialdeman, 1842. 



Shell rather small, whorls few, slowly and regularly increasing, rounded 

 or carinated above and below ; aperture somewhat expanded, lip more or 

 less thickened within; a single persistent set of 6 dentiform 

 lamella at short distance within the aperture. 



^^ 



Fig. 36 



Fig- Z7 



Type: Planorbis ariiiiyenis Say, fig. 35. Aperture,' fig. 36. Radula, fig. 37. 



Sul)family POMPHOLIGIN/E Ball, 1866. 



Shell spiral, dextral, flattened above ; the body whorl very large. 



Animal sinistral. Tentacles moderate, stout, cylindrical, slightly globose 

 at the tips; eyes sessile, near the inner base of the tentacles; foot short, 

 bluntly rounded behind; jaw single, subcordiform; radula with the teeth in 

 nearly horizontal rows, central tooth small, bicuspid, laterals wide. 



Key to the genera of Pornpholigince. 



1. Shell imperforate Pompholyx. 



2. Shell deeply umbilicate Carinifex. 



,;CtT- 



Fig. 38 



Genus POMPHOLYX Lea, 1856. 



Shell spiral, dextral, globosely depressed, imperforate; 

 whorls few, spire short, obtuse; last whorl very wide, ventri- 

 cose; aperture very large, wide, subcircular, expanded; lip 

 thin ; columella thickened. 



Animal as in the subfamily. 



Type : P. cffusa Lea, fig. 38. Radula, fig. 39. 



Fig. 39 



