240 PROCEEDINGS OF THE ACADEMY OF 



Fig. 7. Helix clausa, Say. 



b. Marginal teeth. 



c. Extreme marginals. 

 Fig. 8. Helix dentifera, Binney. 



b. Marginal tooth. 



Plate XIII. 



Fig. 1. Hemitrochus varians, Mke. 



a. Central and first lateral teeth. 



&, c. Marginal teeth. 

 Fig. 2. Helix griseola, Pfr. Same references. 

 Fig. 3. Helix Stearnsiana, Gabb. 



a. Group of central and lateral teeth. 



b. Group of teeth showing transition from laterals to 



marginals. 



c. A group of extreme marginal teeth. 

 Fig. 4. Helix Kelletti, Forbes. 



a. Central and first lateral tooth. 



b. Transition from laterals to marginals. 



c. Extreme marginal tooth. 



Fig. 5. Helix lineata, Say. Same references as in fig. 1. 



b. Marginal tooth. 

 Fig. G. Helix Newberryana, W. G. B. Same references as in fig. 4. 

 Fig. 7. Helix aspersa, Mull. Same references as in fig. 4. 

 Fig. 8. Helix fidelis, Gray. Same references as fig. 4. 

 Fig. 9. Helix infumata, Gld. 



a. Central and first lateral tooth. 

 b, c. Transition teeth from different parts of the membrane. 



d. Extreme marginal teeth. 



&* 



Plate XIV. 



a. Central and lateral teeth. 



b. Transition from laterals to marginals. 



c. Inner marginal teeth. 



d. Outer marginal teeth. 

 Fig. 1. Helix tudiculata, Binn. 

 Fig. 2. Helix arrosa, Gld. 



Fig. 3. Helix ruficincta, Newc. 



Fig. 4. Helix Traski, Newc. 



Fig. 5. Helix sequoieola, J. G. Coop. 



