346 The Molluscan Family Planorbidae 



PLATE 55 



Radulae of Helisoma 

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



1. Helisoma trivolvis (Say). Oneida Lake, New York. 



60, center tooth; 1-7, lateral teeth; 8-10, intermediate teeth; 11-18, marginal 

 teeth. 



2. Helisoma trivolvis {Sa.y) ^ pseudotrivolvis F. C. Baker, near lentum Say. From 



Reelfoot Lake, Tennessee. 

 150, center tooth; 1-7, lateral teeth; 8-10, intermediate teeth; 11-13, marginal 

 teeth. 



3. Helisoma trivolvis lejitum (S&y) ^ pseudotrivolvis F. C. Baker. Reelfoot Lake, 



Tennessee. 

 107, center tooth; 1-7, lateral teeth; 8-10, intermediate teeth; 11-14, marginal 

 teeth; 50, 50th center tooth of another row. 



4. Helisoma trivolvis (Say). Sturgeon Bay, Wisconsin. 



70, center tooth; 1-6, lateral teeth; 7-11, intermediate teeth; 13, 14, marginal 

 teeth. 



5. Helisoma chautauquense F. C. Baker. Chautauqua Lake, New York. 



102, center tooth; 1-7, lateral teeth; 8-11, intermediate teeth; 12-15, marginal 

 teeth. 



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



96, center tooth; 1-8, lateral teeth; 9-11, intermediate teeth; 12-15, marginal 

 teeth. 



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



16-25, marginal teeth; 4, 4th lateral tooth from another row, with two entoconic 

 cusps. 



