I44 Allen, Origin and Distribution of N. A. Birds. 



Auk 

 April 



America with those employed by Dr. Merriam in his recent well- 

 known admirable papers on the geographical distribution of North 

 American mammals, so frequently cited in the preceding pages, 

 it will be noticed that there is a striking agreement in their num- 

 ber and boundaries, although a few new minor divisions have 

 here been introduced ; yet the terms employed for their designation 

 are to a great extent different. As already intimated, the present 

 system of classification and nomenclature is a further develop- 

 ment of that first instituted by me in 1871, and used later in 1878, 

 and now carried out in greater detail and extended to the whole 

 North American Continent. The present revision of the subject 

 is therefore not to be looked upon as unfriendly criticism of Dr. 

 Merriam's classification and nomenclature, which he evidently 

 adopted provisionally, 1 selecting such terms as would suffice 

 to clearly indicate the areas under discussion ; his attention was 

 given mainly and most successfully to an elucidation of the facts 

 of distribution ; a detailed consideration of the nomenclature of 

 the subject was outside of his special field. 



In attempting to establish a consistent scheme of classification 

 and terminology, the aim is to assign definite terms for areas of 

 similar taxonomic grade. Many of the terms in more or less 

 current use have been employed so loosely, and used in so many 

 different senses by different writers, that, as already said, a strict 

 'rule of priority' cannot be enforced, at least without leading in 

 many instances to very unsatisfactory and inharmonious results. 

 As already explained, the system here adopted is analogous to 

 the schemes followed in systematic biology and stratigraphic 

 geology. In the selection of names for the higher divisions, 

 reference has been had to the influences controling the geo- 

 graphic distribution of life, namely, climate, and the climatic 

 zones have been allowed to suggest the names of many of the 

 major ontological areas. Indeed, such names have been employed 

 before in nearly the same sense, not only by physical geographers, 

 but by many botanists and some zoologists. Thus 'Humid' and 

 'Arid' become appropriate and suggestive designations for the 

 eastern and western subdivisions of the North American Warm 

 Temperate Subregion. For the lesser regions geographical 



1 This is not only apparent from his papers, but I am informed by him that this was 

 intentionally the case. 



