22 Bryant Wai^ker 



Siibfamil.y NEOPLANORBIN^ Hannibal, 1912. 

 Shell small, planorbiform or neritiform. 



Key to the genera of Neoplanorbin<c. 



Shell planorbiform Neoplanorbis. 



Shell neritiform Amphigyra. 



Genus NEOPLANORBIS Pilsbry, 1906. 



Shell very minute, planorboid, dextral, subdiscoidal, 

 nearly flat above, convex below, usually carinate at the 

 periphery; whorls two, rapidly enlarging; aperture very 

 oblique, wider than high, a little dilated at the base; lip 

 thin, not continuous; columellar margin straight and 

 broadly dilated, somewhat thickened within. Dentition and anatomy so far 

 as known similar to Aiiiphigyra. 



Type: -V. taufiHus Pils., fig. 67. 



Fig. 67 



Genus ATvIPHTGYRA Pilsbry, 1906. 



Shell minute, dextral^ neritoid or 

 crepiduliform, imperforate, with a small, 

 depressed, lateral spire ; whorls about 

 i}4, very rapidly enlarging, the last very 

 convex dorsally ; apex smooth ; body- 

 whorl spirally striate ; aperture very 

 large, transversely oval ; lip continuous and full, thin ; cavity of the spire 

 very small, a thin, broad, concave, columellar plate projecting across the end 

 next the spire. 



Fig. 68 



Fig. 69 



Animal sinistral, externally lymnasid ; tentacles short, blunt, cylindric ; 

 eyes near their inner bases ; a short, false gill in the pallial cavity. Radula ar- 

 ranged as in Lymncca, central tooth unicuspid, laterals bicuspid, marginals 

 low, wide, with four or five cusps. 



Type: A. alaharncnsis Pils., fig. 68. Radula, fig. 69. 



