JVorth American Helices. 21 



pura Alder. unidentata Say 



Syn. electrina Gould. is indentata Say. 



vortex Pfr. 



In the above lists incongruous forir.s both of shell and animal 

 are placed together, allied forms are separated, and in several 

 cases the names of species are repeated in different genera or 

 sub-genera, and even in different families. 



Among other characteristics of the Fam. Helicidse, H. & A. 

 Adams give : — " foot elongated, with the hind part simple and 

 pointed behind, not glandiferous" (II. 126) ; and of the Fam. 

 Stenopidse : " foot long and narrow, abruptly truncated behind, 

 and furnished with a distinct, mucous, caudal gland" (II. 221) ; 

 yet I find in the lists above quoted the following inconsist- 

 encies : — 



Fam. Helicidse. Fam. Stenopidse. 



Ancbistoma hirsutum Say. Zonites stenotrema Fer. 



Iberus electrinus Gould. Helicella pura Alder. 



" sportella Gould. Discus Vancouverensis Lea. 

 Hygromia planorboides Raf. " plauorboides Raf. 



Looking at the lists of species in the different genera and sub- 

 genera, I notice : — 



Ancbistoma cereolus Muhlf. ) Polygyra septemvolva Say. 



" volvoxis Parr, j 



" major Binn. Mesodon albolabris Say. 



" palliatum Say. " appressum Say. 



" Troostianum Lea. Polygyra fastigiatum Say. 



Zonites fuliginosa Griff. Helicella fuliginosa Griff. 



The arrangement of the North American Helices by Albers 

 (Die Heliceen, 2d ed.) is certainly far more reliable and con- 

 sistent than that of H. & A. Adams. It is based on a better 

 knowledge of their forms and of the characters of the animals. 

 The lists* given by the former are not simply alphabetical, as 

 are those of the latter, but the affinities of the species are con- 



* It will be understood that I extract from the lists given in both the works 

 referred to the names only (with few exceptions) of the species which occur iu 

 North America exclusive of the Pacific Coast and Mexico. 



