352 The Molluscan Family Plauorbidae 



PLATE 58 



Radulae of Helisoma 



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



L Helisoma whiteavesi F. C. Baker. Mille Lacs, Ontario, Canada. 



105, center tooth; 1-16, lateral teeth; 17-19, intermediate teeth; 20-35, marginal 

 teeth. 23, a pathologic tooth in another row. 12, a lateral tooth on the left 

 side with split cusps. 



2. Helisoma corpuhntum vermilionense F. C. Baker. Vermilion Lake, Minnesota. 



101, center tooth; 1-7, lateral teeth; 9-12, intermediate teeth; 13-21, marginal 

 teeth. 



3. Helisoma corpulent um inidticostatum F. C. Baker. Kahniinminanikok Lake, 



Ontario, Canada. 

 60, center tooth; 1-7, lateral teeth; 11-14, intermediate teeth; 15-41, marginal 

 teeth. 



4. Helisoma plexatum (Ingersoll). Teton River, near Rexburg, Idaho. 



44, center tooth; 1-8, lateral teeth, 1 and 4 with mesocones worn or pathologic; 

 10-13, intermediate teeth; 13-16, marginal teeth. The two 13 figures show 

 how this tooth differed in two rows, being an intermediate tooth in one row 

 and a marginal tooth in another row. 



5. Helisoma plexatum (Inger.soll). 



The 120th row in another membrane from a Teton River specimen. 16-18, 

 modified marginal teeth. 



6. Helisoma plexatum (Ingersoll). Smartweed Lake, Colorado. 



13, a lateral tooth; 14-15, marginal teeth. 



