444 NATURAL SCIENCE. June. 



The following statement, giving statistics derived from the pre- 

 ceding lists, will complete the information necessary for a comparative 

 view of the relations of the Palaearctic and Nearctic Regions as 

 regards their land-birds : — 



The Palaearctic 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 32 families of land-birds. 

 Of fhese, 8 families are not in the Palaearctic Region. 

 These 8 families comprise 40 genera and 128 species. 



The 118 Palaearctic 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 between any other two regions which are conter- 

 minous with each other. The most striking relation of the Palaearctic 

 and Nearctic Regions is, therefore, not their resemblance, 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 characteristic groups of the Eastern Hemi- 

 sphere 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 Icteridse, and the Tyrannidae, containing between 

 them nearly a hundred species. Now as there are only 417 species 

 of land-birds in the whole Nearctic Region, we find that between 

 One-tllird and one-fourth, of the whole belong to families which 

 are entirely foreign to the Palaearctic Region. It may be confidently 

 asserted that none of the other regions can be so divided that the 

 two parts shall show an amount of difference at all approaching to 

 this. Yet it is proposed to unite these two regions because they 

 are not sufficiently distinct. They are, however, very much more 

 distinct than are the Ethiopian and Oriental Regions, though the 

 former includes the isolated and peculiar Madagascar fauna. Less 

 than one-twelfth of the Ethiopian families of land-birds are not 

 Oriental, while only one-ninth of the Oriental families are not 



