354 The Molluscan Family Planorbidae 



PLATE 59 



Radulae of Helisoma 

 See remarks on plate 53. Line at bottom of plate indicates 25 microns in length. 



1. Helisoma plexatum (Ingersoll). Grand Mesa, Colorado. 



60, center tooth; 1-12, lateral teeth; 13-17, intermediate teeth; 18-22, marginal 

 teeth. 



2. Helisoma plexatum (Ingersoll). Columbine Lake, Colorado. 



95, center tooth; 1-10, lateral teeth; 11-12, intermediate teeth; 13-15, marginal 



teeth. 



3. Helisoma tenue calijorniense F. C. Baker. San Bernardino Mts., California. 



Normal teeth. 60, center tooth; 1-11, lateral teeth; 12, 13, intermediate teeth; 

 14-21, marginal teeth. 



4. Helisoma tenue calijorniense F. C. Baker. San Bernardino Mts., California. 



Abnormal teeth, the lateral teeth with extra cusps on both entocones and ecto- 

 cones and with mesocone much modified. 60, center tooth; 1-10, lateral 

 teeth; 11, 12, intermediate teeth; 12-17, marginal teeth. 



5. Helisoma subcrenatum (P. P. Carpenter). Variety. Pass Lake, Puget Sound, Wash- 



ington. 



96, center tooth; 1-15, lateral teeth; 16-18, intermediate teeth; 19-28, marginal 



teeth. 



6. Helisoma tenue calijorniense F. C. Baker. San Bernardino Mts., California. 



An abnormal 11th lateral tooth. 



