84 Cincinnati Society of Natural History. 



marginal. The dentition is very similar to that of L caperata. 

 A large number of specimen have been examined. 



IytMN physa palustris Miiller. Plate IV, D. 



Radula formula ff + * + | + \ + % -f f + ff (34- 1 - 34) I 

 teeth as usual; laterals bicuspid; transition teeth at first 

 like laterals, but tricuspid, the central cusp the largest (11), 

 but soon (13) the inner cusps become more equal and the 

 outer cusp smaller ; marginal teeth of the usual type. A 

 single membrane (D) had the first lateral to the right of the 

 central tooth with a bifid outer cusp. This was observed in 

 all the first laterals of this membrane. 



LiMNOPiiYSA palustris m ichiganensis Bryant Walker. 

 Radula not differing from the typical form. 



LlMNOPHYSA REFLKXA Say. 



Radula formula + f + \° + \ + V° + 1 + ff (40-1-40); 

 teeth similar to those of palustris; there is very little varia- 

 tion in the form of the teeth in this species. 



LlMNOPHYSA REFEEXA ATTENUATA Say. 



Radula not essentially differing from typical rcflexa. 



Limn.EA stagnalis Linne. 



Radula formula + + V 3 + { + ¥ + "W+if (4 6 " 1 

 -46) ; teeth as usual. The writer has examined several mem- 

 branes of this species and the number of teeth vary from 

 46-1-46 to 54-1-54. Binney (L. & Fr. W. Shells, p. 28) gives 

 40-1-40 and (p. 155) 47-1-47 teeth ; Bland and Binney (Amer. 

 Journ. Conch, Vol. VIII, p. 161) give 40-1-40. It is probable 

 that the membrane having 54-1-54 teeth was abnormal. 

 46-1-46 is the number generally found. 



4 



