362 The Molluscan Family Planorbidae 



PLATE 63 



Radulae of Helisoma 



See remarks on plate 53. Line at lower right of plate 

 indicates 25 microns in length. 



1. Helisoma trivolvis fallax (Haldeman). Cambridge, Massachusetts. 



60, center tooth; 1-7, lateral teeth; 10, intermediate tooth; 11-23, marginal teeth. 



2. Helisoma tenue californiense F. C. Baker. Shandon, California. 



77, center tooth; 1-11, lateral teeth; 12. intermediate tooth; 13-19, marginal teeth. 

 100th row. Numerals 1-11, lateral teeth with multiple cusps on entocone and 

 ectocone. 



3. Helisoma trivolvis lentum (Say). New Orleans, Louisiana. 



60, center tooth; 1-9, lateral teeth; 10, 11, intermediate teeth; 12-20, marginal 

 teeth. 



4. Helisoma duryi eudiscus Pilsbry. Silver Springs, Florida. 



84, center tooth; 1-10, lateral teeth; 11, 12, intermediate teeth; 12-22, marginal 

 teeth. 



