342 The Molluscan Family Planorbidae 



PLATE 53 



Radulae of Helisotna 



In the plates of radulae, the number under the central tooth (as 15, 80, 98, 50, and 75 

 on this plate) indicates the number of the transverse row, counting from the front 

 end of the radula. The numbers following indicate the number of the tooth in this 

 row, counting from the central tooth, the first lateral tooth being nvuiiber 1. The line 

 at the lower part of the plate indicates 25 microns. 



1. Helisoma anceps (Menke). Maple River, Michigan. 



15, center tooth; 1-5, lateral teeth; 6, 7, intermediate teeth; 8-14, marginal teeth. 



2. Helisoma anceps (Menke). Chautauqua Lake, New York. 



80, center tooth; 1-5, lateral teeth; 6-8, intermediate teeth; 9-13, marginal teeth. 

 118, center tooth (of 118th row) with first left marginal beside it. 



3. Helisoma anceps (Menke). Unionville, Connecticut. 



98, center tooth; 1, 2, lateral teeth; 6, 7, intermediate teeth; 8, 9, marginal teeth 

 on right side; 11-16, marginal teeth on left side of row. 90, 90th row, center 

 tooth; 5, lateral tooth with two ectocones; 8, intermediate tooth; 9, 10, 

 marginal teeth. 



4. HcILsoma anceps sayi F. C. Baker. Bayfield, Wisconsin. 



50, center tooth in 50th row; 1-5, lateral teeth; 6, 7, intermediate teeth; 8-14, 

 marginal teeth. 75, 75th row, pathologic center tooth; 1-5, pathologic lateral 

 teeth. 



