5S Merriain — (feor/i'(ij>]iic /)ii^hil)iiflon of Life. 



In a cDiiiiiiunicatioii already referred to (North American 

 Fauna, No. .'>, Septemlx'r, 1S<)()) T stated the conclusion that the 

 connnoidy accepted division of the United States into Eastern, 

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

 that " tlie whole of extratro])ical North America [the Nearctic 

 re^-ion of Sclater and ^^'al]ace] consists of hut two primary life 

 regions, a Boreal region, which is circumpolar ; and a Sonoran or 

 Mc.riaiv 7}ihl( -la lid region which is unique." The so-called East- 

 ern Province is mainly of Sonoi-an derivation, comprising the 

 liuniid divisions ()f the Lower Sonoran and Upper Sonoran Zones 

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

 Neutral Piclt connnonly known among ornithologists as tlie 

 Alleglianian fauna. It contains also a southward extension of 

 the P>oreal 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 hetween two northward prolongations of 

 the arid Sonoran, tlie one occui)ying tlie (Jreat Plains, the other 

 the Great Basin. 



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

 ward extension of the Boreal Region which finally liifurcates, 

 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 tif the state and reaches 

 north ill the San Joaquin and Sacramento Valleys. 



Pal,i:akcti(' and Nearctic Regions. 



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

 tlie distribution of life outside of our own continent, hut it so 

 hapiiens that the Boreal element in America resembles that of 

 ICurasia so closely that in the judgment of many eminent 

 authorities the two constitute but a single i)rimary region — a 

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

 nistic to that proj^osed by Sclater * in 1857 and adopted Avith 

 slight modification by Wallace. Sclater considers the whol'e of 

 extratropical North America as constituting a single region, 



■-.louni. l/nm. Sor. (Zool.), II (Cur 1S57), 1S"),S, l:)0-U.^; uml au'ain, with 

 SO)!) • alti'i'.itiiiiis, in !l)is, sixlli series, III, lS!tl, ."'>14-"iri7. 



