'Sgi-I Rccetif Literature. 



97 



Boreal and the Tropical Provinces, antl corresponding to the Warm 

 Temperate Region of some authors. (4) The Tropical Province, ex- 

 tending into North America from the south, and embracing Central 

 America and the Antilles, the lowlands of Mexico, and a narrow coast 

 belt of southern Florida. 



For many years that portion of North America situated mainly within 

 the United States has been divided into a so-called Eastern Province, a 

 Middle Province, and a Western Province. While these 'Provinces' (es- 

 tablished by Baird in 1866) have been hitherto generally accepted, they 

 have been unsatisfactory and troublesome, but have escaped searching 

 analysis till taken in hand by Dr. Merriam in the present paper. Follow- 

 ing the clue furnished by the evident fact that the life of middle North 

 America is made up of increments from both the north and the south, and 

 that tiie boreal element extends far to the southward at the higher eleva- 

 tions, while the life from the south occupies the intervening lowlands, 

 resulting in the interdigitation of areas stocked respectively with north- 

 ern and southern types, it became clear that these long recognized Pro- 

 vinces were untenable, in so far at least as any basis for the so-called 

 'Middle' or 'Central' Province is concerned. This Central Province was 

 made up of the Rocky Mountain region, the Great Plains to the eastward, 

 and the Great Basin to the westward. The Rocky Mountain region evi. 

 dently derived its life from the north, and is essentially a part of the 

 'Boreal' or Cold Temperate life-region. The life of the Great Plains and 

 the Great Basin is as obviously derived mainly from the south, with an 

 intermixture of more or less modified northern elements. With this key 

 to the problem Dr. Merriam has separated his Sonoran Province (which 

 is made to include the whole breadth of the continent) into six 'sub- 

 regions,' as follows : (i) an Arid or Sonoran sub-region, occupying the 

 table-land of Mexico, western Texas, portions of New Mexico, Arizona, 

 and southern California; (2) a Californian sub-region, occupying the 

 greater part of California ; (3) a Lower Californian sub-region; (4) a 

 Great Basin sub-region, embracing the area between the Rocky Moun- 

 tains and the Sierra Nevada, north to the Plains of the Columbia ; (5) a 

 Great Plains sub-region, extending from Northern Texas to the Plains of 

 the Saskatchewan; (6) a Louisianian or Austroriparian sub-region, 

 occupying the eastern United States from the southern border of the 

 Alleghanian Fauna, as commonly recognized, southward to the Gulf 

 coast, and thus equivalent to the Carolinian and Louisianian Faunas, as 

 usually limited by ornithologists. These regions are all shown in colors 

 on Map 5, but the distinguishing elements of each are not stated. They 

 seem, however, fairly tenable, though set forth as merelj' provisional, 

 and presumably open to some modification. Even the terms to desig- 

 nate the relative rank of the various subdivisions are used tentatively, 

 the whole scheme of nomenclature requiring careful attention, since 

 nearly every term employed for the designation of the diff'erent grades of 

 life areas has been used differently by diflferent authors. The matter 



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