Il8 Allen, Origin and Distribution of N. A. Birds. | April 



widely different senses, in accordance with the individual 

 preferences of different writers. The terms realm, region, king- 

 dom, province, district, and fauna have sometimes been 

 applied by different writers to nearly the same geographical 

 area, and each of them to divisions considered as of primary 

 rank, while most of them have also been used for regions of 

 secondary or still lower grade. In many cases they have been 

 used merely in a quasi-technical sense, and there is hence diffi- 

 culty in determining their claims to recognition by any rule of 

 priority, or by frequency of use in any particular sense ; so we 

 are forced to choose mainly on grounds of appropriateness and 

 convenience, the main thing being to secure uniformity of 

 application. In view of this unfortunate state of affairs I 

 attempted, in a paper on the geographical distribution of North 

 American birds, published in 1871, 1 to devise a system of terms 

 that should be not only appropriate, but in as close conformity as 

 possible with previous usage. Finding that realm had been 

 used by Agassiz and others for regions of the first rank, and that 

 region and province had generally been employed for ai - eas of 

 secondary or lower rank, I proposed a scheme of nomenclature, 

 which to some extent has been followed by others, but of course 

 not fully or rigidly, since little attention has been paid to exact 

 terminology in geographical biology. The scheme then proposed 

 is as follows : — 



For divisions of the first rank, Realm. 

 " " " second rank, Region. 



" " " third " Province. 



" " " fourth " Subprovince or District. 



" " "• fifth " Fauna. 



Their grade and order of sequence may be indicated by a 

 comparison with the leading groups in zoology ; thus realm 

 would correspond in rank with class; region with order; 

 province with family ; district with genus ; fauna (ox flora, 

 as the case may be) with species. It sometimes becomes con- 

 venient to recognize other divisions intermediate to these — as in 

 zoology we have suborder, subfamily, subgenus, and sub- 



1 Bull. Mus. Comp. Zool., II, No. 3, April, 1871. 



