58 Merriam Geographic Distribution of Life. 



In a communication already referred to (North American 

 Fauna, No. 3, September, 1890) I stated the conclusion that the 

 commonly accepted division of the United States into Eastern, 

 Middle, and Western Provinces had no existence in nature, and 

 that " the whole of extratropical North America [the Nearetic 

 region of Sclater and Wallace] consists of hut two primary life 

 regions, a Boreal region, which is circum polar ; and a S<nntran or 

 Mexican Table-land region which is unique." The so-called East- 

 ern Province is mainly of Sonoran derivation, comprising the 

 humid divisions of the Lower Sonoran and Upper Sonoran Zones 

 (Austroriparian and Carolinian faunas), and of the Transition or 

 Neutral Belt commonly known among ornithologists as the 

 Alleghanian fauna. It contains also a southward extension of 

 the Boreal Region along the Appalachian mountain system 

 mainly in the form of isolated islands. 



The so-called Central Region in like manner is made up of a 

 southward extension of the Boreal Region along the Rocky Moun- 

 ain plateau, enclosed between two northward prolongations of 

 the arid Sonoran, the one occupying the Great Plains, the other 

 the Great Basin. 



The so-called Pacific or Western Province consists of a south- 

 ward extension of the Boreal Region which finally bifurcates, 

 sending a long arm south over the Cascade Range and the Sierra , 

 Nevada, and a secondary and shorter arm along the Pacific coast 

 north of San Francisco, together with a Sonoran element which 

 covers nearly the whole southern part of the state and reaches 

 north in the San Joaquin and Sacramento Valleys. 



PAL^ARCTIC AND NEARCTIC REGIONS. 



It is no part of the purpose of the present address to discuss 

 the distribution of life outside of our own continent, but it so 

 happens that the Boreal element in America resembles that of 

 Eurasia so closely that in the judgment of many eminent 

 authorities the two constitute but a single primary region 'a 

 view in which I heartily concur. This arrangement is antago- 

 nistic to that proposed by Sclater* in 1857 and adopted with 

 slight modification by Wallace. Sclater considers the whole of 

 extratropical North America as constituting a single region. 



*.Touni. Linn. Soc. (Zool.), II (for 1S57), 185X, 1:50-145; and ajriiin, with 

 some alterations, in Ihis, sixth scries, III, 1X1)1, 514-557. 



