IA2 Allen, Origin and Distribution of N. A. Birds. I April 



Glaucidium hoskinsi Dendroica bryanti 



Crotophaga sulcirostris Geothlypis beldingi 



Dryobates scalaris lucasanus Harporhynchus cinereus 



Basilinna xantusi Campylorhynchus affinis 



Empidonax cineritius Merula confinis 

 Empidonax griseus 



A few additional subspecies of northern forms also characterize 

 the subtropical portion of the peninsula, which may perhaps well 

 bear the name Saint Lucas Fauna. 



Independently of the subdivisions already enumerated, and in 

 addition to them, North America may be divided into a number 

 of transcontinental belts or Zones in accordance with the climatic 

 conditions prevailing over the different parts of the continent. 

 Several of these zones have been repeatedly recognized by various 

 writers on the distribution of animals and plants. A division of 

 extra-tropical North America into about seven zones will greatly 

 facilitate the correlation of the fauna? of different regions. These 

 are, (1) the Arctic or Hyperborean Zone, equivalent to the 

 American portion of the Arctic Realm ; (2) the Subarctic or 

 Hudsonian Zone ; (3) the Cold Temperate or Canadian Zone; 

 (4) the North Warm Temperate or Alleghanian Zone; (5) 

 the Middle Warm Temperate or Carolinian Zone ; (6) the 

 South Warm Temperate or Louisianian Zone; (7) the Sub- 

 tropical or Floridian Zone. 1 Dr. Merriam has already in his 

 recent papers on the distribution of North American mammals 

 distinguished these zones more or less definitely in treating of the 

 life zones of the San Francisco Mountain region in Arizona and 

 in Idaho. He has done much also toward correlating the life 

 zones of mountain faunas with the long recognized faunae of the 

 Atlantic Coast. Much further information is required before 

 these zones can be geographically defined over the western half 

 of the continent. 



In selecting names for their designation several alternatives 

 present themselves, as for example, names derived from the 

 climatic zones, or from some leading characteristic, as 'Spruce 



> This is a modification of my recently published classification (Bull. Am. Mus. 

 Nat. Hist., IV, p. 240), rendered necessary from the evident desirability of reserving 

 the term 'Subtropical Zone' for the designation of the most northern belt of the 

 Tropical Realm, instead of applying it to the lowest or most southern belt of the 

 Temperate Realm, as is done when it is used for the Louisianian Zone. 



