On Prophysaon, etc. 301 



ArioUmax niger, J. G. Cooper, I. c. 149, pi. iii, iSg. E, 1-4. 

 San Francisco Bay. An examination of the original 

 specimens belonging to the State collection of California 

 convinced us of this being a distinct species. The 

 anatomy, especially the genitalia, of these species varies 

 greatly, as we hope to show in a future paper. 



On the Generic Position of Helix lycltiiaicSilis, 311111. 



Prominent among the group of Helices known as Dentel- 

 lai'ia is Helix lycJmuchus, Miiller, a species well known from 

 its characteristic shell. " Though its specific identity is un- 

 questioned, it has been less fortunate with respect to generic 

 position. From an examination of the generative organs 

 and jaw, this species was referred by M. de St. Simon 

 (Journ. de Conch. Ill, p. 227, Aug., 1853) to the genus 

 Zonites. So positively was this determination made that it 

 has been accepted by subsequent authors, either absolutely 

 or to a degree sufficient to throw doubt upon the species 

 being a true Helix. Thus in the second edition of Albers' 

 "Die Heliceen," p. 79, there is a paragraph fixing the place 

 it would hold as a distinct genus among the Vilrinea, should 

 St. Simon's observations be confirmed ; and quite recently 

 we find it singled out l^y Messrs. Fischer and Crosse (Moll. 

 Mex. et Guat., p. 205) as an instance of the shell of a 

 terrestrial mollusk beiuo^ unreliable in indicatins: sfeneric 

 position. 



Early in our studies of the classification of land shells, we 

 were inclined to doubt the correctness of St. Simon's decis- 

 ion. On consulting his paper (p. 234) we noticed that he 

 placed Helix lychnuchus in Zonites simply because he ac- 

 cepted Moquin-Tandon's decision that Zonites is generically 

 distinct from Helix, in having (1) a jaw without ribs or 

 marginal denticnlatlons and with a median rostriform pro- 

 jection to its cutting edge; and (2) by the absence of dart, 

 dart sac and multifid vesicles in the generative system. We 

 had satisfied ourselves that this distinction does not exist, 



