V I 8 I ' X '] Allen, Origin and Distribution of N, A. Birds. I A J 



life areas in a country where there are no impassable physical 

 barriers to prevent the diffusion of animals and plants." 1 



Dr. Merriam's generalizations respecting the Central Province 

 of authors mark an important advance in the study of North 

 American bio-geography. Taking this region with its original 

 boundaries and significance it is a highly artificial division, em- 

 bracing within its area very unlike faunal elements. Eliminating 

 from it, however, the broad central arm of the 'Boreal' or Cold 

 Temperate Subregion, which occupies so much of the great 

 central plateau, relieves it of an extraneous element, and reduces 

 it to a more natural and geographically quite different region. 



The first discrepancy between Dr. Merriam's classification and 

 my own that requires notice is in respect to the primary divisions 

 of the North American Region, which he first termed 'Provinces' 2 

 and later 'Regions,' 3 with the prefixes 'Boreal' and 'Sonoran' 

 respectively for the 'Cold Temperate' and 'Warm Temperate' 

 Subregions of the present writer. The use of Boreal, however, 

 as shown above, was not an innovation ; but the term 'Sonoran' 

 was used in a new and greatly extended sense, the term Sonoran 

 being applied to a region identical in geographical extent with 

 the Warm Temperate, — a designation previously used for the 

 same area, — and hence including the region east of the Mis- 

 sissippi (as well as that west of it), from the Great Lakes and 

 southern New England south to Florida and the Gulf Coast. 

 The terms 'Sonoran' and 'Sonoran Province' were used as early 

 as 1866 by Prof. Cope, 4 and also later by Cope, Heilprin, and 

 others, for a region of comparatively small extent, consisting of 

 Sonora and adjoining portions of Arizona and New Mexico. In 

 1S87 Heilprin 5 extended the region to include "the peninsula of 

 Lower California, the State of Sonora in Mexico, New Mexico, 

 Arizona, and parts, not yet absolutely defined, of Nevada, Cali- 

 fornia, Texas, and Florida," and modified its title by calling it the 

 'Sonoran Transition Region.' The Sonoran Province or Region 

 of these authors is thus not at all the 'Sonoran Region' of Mer- 

 riam, which is an area of much greater extent and of higher rank. 



1 N. Am. Fauna, No. 3, pp. 22, 23. 



2 N. Am. Fauna, No. 3, p. 19, 20. 



3 Proc. Biol. Soc. Washington, VII, 1892, pp. 22, 26. 



4 Proc. Acad. Nat. Sci. Phila., 1866, p. 300. 



5 The Geogr. and Geo!. Distrib. of Anim., p. 106. 



