THE PAL^ARCTIC AND NEARCTIC REGIONS 247 



The following statement, giving statistics derived from 

 the preceding lists, will complete the information neces- 

 sary for a comparative view of the relations of the Palae- 

 arctic and Nearctic Regions as regards their land-birds : — 



The Palsearctic Region has 36 families of land-birds. 

 Of these, 12 families are not in the Nearctic Region. 

 These 12 families comprise 22 genera and 57 species. 



The Nearctic Region has 3 2 families of land-birds. 

 Of these, 8 families are not in the Palsearctic Region. 

 These 8 families comprise 40 genera and 128 species. 



The 118 Palsearctic genera which are not Nearctic 



comprise 472 species. 

 The 113 Nearctic genera which are not Palaearctic 



comprise 282 species. 



The preceding lists and figures enable us to obtain a 

 very complete view of the amount of difference that exists 

 between the avifaunas of the Palaearctic and Nearctic 

 Regions. 



Considering first the Family groups, we find that in the 

 one case one-third and in the other one-fourth of the 

 families of the one region are not found in the other ; and 

 this is an amount of difference that does not occur be- 

 tween any other two regions which are conterminous 

 with each other. The most striking relation of the Palae- 

 arctic and Nearctic Regions is, therefore, not their re- 

 semblance, but their dissimilarity. 



Again, the 12 families which thus differentiate the 

 Palaearctic Region from the Nearctic comprise 22 genera 

 and 57 species ; and among them we find such charac- 

 teristic groups of the Eastern Hemisphere as the accentors, 

 the flycatchers, the starlings, the vultures, and the sand- 

 grouse, — families entirely absent from the whole Western 

 Hemisphere. 



The 8 families which differentiate the Nearctic Region 

 from the Palaearctic are even more important, since they 

 contain 40 genera and 128 species; and include such 

 characteristic New World types as the Mniotiltidae, the 

 Icteridae, and the Tyrannidae, containing between them 



