A MANUAL OF AMERICAN LAND SHELLS. " 19 



Tlie bouudaries of these proviuces and the subdivisions which appeal 

 to exist in them will be given below, as well as lists of their peculiar 

 si>ecies. It must be distinctly understood, however, that future re- 

 searches, especially at the South and Southwest, may greatly modify 

 the views here j) resented. 



I. — The Pacific Province* com j)rises a narrow strip between the Sierra 

 Nevada and Cascade Mountains on the east and the Pacific Ocean on 

 the west. Its southern limit is San Diego, from whence it extends north- 

 erly into Alaska. 



Over the whole length of this province, confined, however, to the 

 neighborhood of the coast, the following species range : 



Macrocyclis Vancouverensis. Prophysaon Hemphilli. 



sportella. Succmea rnsticana. 

 Mesodon Columhianus. Oregonensis. 



germanus. Nuttalliana. 



Arionta tudiculata, Onehidella Carpenteri. 

 Ariolimax Columhianus. 



Over the whole of this province we find also the following species 

 common to Eastern Korth America. They also extend over the whole 

 northern portion of the continent where the mountains, by their lower 

 altitude, are not barriers to distribution. It is, no doubt, from these 

 regions that they have spread through the Pacific Province, and not 

 westward over the Eocky Mountains. Had other Eastern species ex- 

 tended over the boreal regions, we should, no doubt, have found them 

 also spreading into the Pacific States. They are especially found along 

 the Sierra Nevada. 



Zonites arboreus. Limax campestris? 



indentatus. Patula striatella. 



minusGulus. Helicodiscus lineatus. 



milium. Micropliysa minutissima. 



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- 



* A most interesting acconnt of this fauna is given by Dr. J. G. Cooper: " On the 

 Distribution and Localities of West Coast Helicoid Land Shells " (Am. Journ. of 

 Couch., II, p. 211, with a map), 



