GEOGRAPHICAL DISTRIBUTION. 19 



They have also spread southward over the Central and Eastern Prov- 

 inces, and now inhabit most, if not all, of North America. They are 



Zonites fulvus. Ferussacia subcylindrica. 



Other species will probably be added to this list by further search ; 

 among them Vallonia jndchella. 



In dealing with the species from the North in Eastern North Amer- 

 ica (see below, p. 27), the question of their distribution will be more 

 fully discussed. 



In addition to the species already enumerated as common to the 

 whole Pacific Province, there are many more restricted in their range. 

 It appears that the Pacific Province is divided into two regions, (a) the 

 Oregonian and (6) Californian, the two intermingling slightly or over- 

 lapping in the extreme north of California, near Humboldt Bay. The 

 faunas of these regions are nearly allied. 



(a) The Oregon Region lies between the Cascade Mountains and the 

 Pacific Ocean, extending northerly through British Columbia into Alaska. 



The following species are peculiar to it :* — - 



Zonites Stearnsi. Arionta Townsendiana. 



Microphysa Lansingi. Arion foliolatus ? 



Mesodon devia. Hemphillia glandulosa. 



Aglaja fidelis. Succinea Hawkinsi. 



There seems to be here some overlapping of the Pacific and Central 

 Provinces, as Arionta Townsendiana, Mesodon devia, and Macrocyclis 

 Vancouverensis extend along the mountains southeasterly into Idaho 

 and Montana. The former two become much dwarfed in size at their 

 most eastern range. 



(6.) The Californian Region extends from Humboldt Bay to San 

 Diego, between the Sierra Navada and Cascade Mountains on the east, 

 and the Pacific Ocean on the west. 



The following are the species peculiar to it : — 



Macrocyclis Voyana. Zonites chersinellus. 



Duranti. Limax Hewstoni. 



Vitrina Pfeifferi. Binneya notabilis. 



Zonites Whitneyi. Ariolimax Californicus. 

 conspectus. niger. 



1 T formerly omitted Onchidclla borealis, Dall, from Sitka, being doubtful whether the 

 genus should be treated as American. More recently I have had reason to include it in 

 my work ; see below. 



