MUSEUM OF COMPARATIVE ZOOLOGY. 197 



be barriers to • 1 '- i ~' K 'ition. It is, no doubt, from these regions that 

 they have spread through the Pacific Province, and not westward over 

 the Rocky Mountains. Had other eastern species extended over the 

 boreal regions, we should, no doubt, have found tbem also spreading into 

 the Pacific States. They are especially found along the Sierra Nevada. 



Zonites arboreus. Limax campestris. 



indentatus. Patula striatella. 



minusculus. Helix liueata. 



milium. Punctum minutissimum. 



In the Pacific Province we also find several species common to the 

 circumpolar regions of Asia, Europe, and America. They have like- 

 wise spread southward along the Sierra Nevada and on either side of it. 

 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. Cionella subcylindrica. 



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

 among them Helix jndchella. 



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

 ica (see below, p. 204), 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 (b) 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 hito 

 Alaska. The following species are peculiar to it : — * 



Helix devia. Arion foliolatus. 



fidelis. Hemphillia ^landulosa. 



Townsendiana. Succinea Hawkinsi. 



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

 Provinces, as Helix Townsendiana, Helix devia, and Macroryclis Van- 



* I omit Onchidella borealis, Dull, from Sitka, being doubtful whether the geuus 

 should be treated as American. 



