' of North American Jlelicidce. 123 



The four species liaving teeth, comprised in W. G. Binnej's 

 Pacific Coast List, are II. gennana Gould, allied to II. monodon 

 Rack., but without the fulcrum, belonging to the foregoing sec- 

 tion 5 ; II. devia Gould, to section 8 ; II. acutedentata AY. G, 

 By., to 13, assuming from its affinity with II. Ariadne that it 

 has no fulcrum, and II loricata Gould, which has a well 

 developed tubercle, belonging to section 17. To these may be 

 added H. Mullani Bland and Cooper (sec. 9), and II. polygy- 

 rella Bid, and Coop., wdiich, unlike any other North American 

 species, has, with an unreflected lip, a parietal tooth and two 

 series of three teeth in each within the last whorl. 



Note on Variation in Species of Helix in Eastern North 



America, 



It will be seen from the foregoing remarks that many of the 

 species of Helix inhabiting Eastern North America are subject 

 to considerable variation. Without entering upon the question 

 of causes of variation, I should notice that, with the exception 

 of size, the variability of shells is rather in ornamentation than 

 in characters which indicate differences in the structure of the 

 animals, or can affect their welfare. 



The variations referred to are chiefly in size, color, sculpture, 

 and degree of the angulation of the periphery. 



Wollaston (On the Variation of Species, p. 106) refers to the 

 tendency exhibited by many Helices to have at least two 

 abruptly marked forms, a larger and a smaller one. He says — 

 "I have indeed been shown specimens by Sir Chas. Lyell of 

 the //. hirsuta Say from N. America, one state of which is 

 considerably more than double the dimensions of the other ; 

 and I believe it is a well known fact that intermediate links 

 have not yet been observed to connect the extremes." So far, 

 however, as my experience teaches, I must say that, without 

 exception, the extremes in N. American Hehces are connected 

 by others of intermediate sizes. 



