VALVATA TRICARINATA. 5 



Richardson as far north as Methy lake, in lati- 

 tude 57. The New England specimens are 

 smaller than those of the Middle States. 



"Var. SIMPLEX, without the keels. Professors Bene- 

 dict and Adams have found this species in Vermont; 

 and in very many instances it is perfectly simple and 

 cylindrical, individuals occurring with every degree 

 of carination, showing that it is still the same species.* 

 In this state, the large tunnel-shaped umbilicus is the 

 best characteristic." Gould. 



VAR. ? BICARINATA, Lea. Proceedings Am. Phil. 

 Soc., vol. ii. p. 83. "Testa orbiculari, superne planu- 

 lata, bicarinata, subcrassa*, superne cornea, inferne al- 

 bida, late umbilicatS; suturis impressis; spira; depressa; 

 anfractibus quaternis, convexis; apertura rotunda, intus 

 albidl Hab. Schuylkill river." Lea. 



Mr. Lea informs me that the soft parts pre- 

 sent a specific distinction, notwithstanding the 

 similarity of the shell with tricarinata ami its 

 varieties. 



VAR. ? UNICARINATA, De Kay, Zool. of New 

 York. 



* " Varieties occur in which the middle carina is obso- 

 lete, or in which none are very distinct." Adams. 



H 2 



