344 The Molluscan Family Planorbidae 



PLATE 54 



Radulae of Helisoma 



See remarks on plate 53. Line at bottom of plate indicates 

 25 microns in length. 



L Helisoma nnceps percarinatum (Walker). Douglas Lake, Michigan. 



85, center tooth; 1-6, lateral teeth; 7-9, intermediate teeth; 10-23, marginal teeth. 

 100, 100th row, center tooth; 1-3, lateral teeth, pathologic (2 entocones) ; 

 9, intermediate tooth; 10, marginal tooth. 



2. Helisoma anceps royalense (Walker). Bamiji Lake, Ontario, Canada. 



60, center tooth; 1-6, lateral teeth; 7-9, intermediate teeth; 10-19, marginal 

 teeth. 



3. Helisoma anceps cahni F. C. Baker. Big Muskallonge Lake, Wisconsin. 



60, center tooth; 1-6, lateral teeth; 7-9, intermediate teeth; 10-18, marginal teeth. 



4. Helisoma anceps latchjordi (Pilsbry). Meach Lake, Quebec, Canada. 



51, center tooth; 1-6, lateral teeth; 7-9, intermediate teeth; 10-26, marginal teeth. 

 60, an abnormal center tooth from another membrane, with accessory lateral 

 cusps above the normal center cusps. 



