GEOGRAPHICAL DISTRIBUTION 



329 



species, Vireomdse, by 1 genus and 1 4 species, Ideridse by 8 genera and 

 21 species, and Tyrannidai by 10 genera and 26 species. The first of 

 these, however, can alone be regarded as eminently characteristic of 

 the area, since that affords a home to all but 3 of the genera, but 

 at the same time only about half of the described species occur 

 there. None of the rest can comj)are with it in this respect, Vir- 

 eonidm having some 5 genera and 50 species, Ideridx more than 20 

 genera and more than 100 species, and Tyrannidm some 70 genera 

 and over 300 species in the Neotropical Region. 



If we extend our investigation from the Families to the genera, 

 we shall come to results which point the same way. It is confessedly 

 difficult to make any accurate comparison owing to the tendency 

 (not Avholly modern) of ornithologists to propose the foundation of 

 genera on very slight excuse ; but, taking the number of Nearctic 

 genera at 330, which was a very liberal estimate toward the end of 

 the period signalized by the labours of the late Prof. S. F. Baird, not 

 more than two dozen of them seem to be peculiar to the Nearctic 

 area,^ while this has about 128 genera in common Avith the Pal^earctic 

 area and 178 which are also Neotropical. The genera peculiar to 

 the New World, occurring both in the Nearctic area and in the 

 Neotropical Region, wdthout appearing in the Palaearctic area, must 

 be divided into two categories in order to obtain a just estimate of 

 the relations of the first tAvo districts. These categories consist of 

 (1) those genera which being only Avinter visitants to the Southern 

 Region are not natives of it, and (2) those which breeding in both 

 districts may fairh" be called common to both. The former, some 

 27 in all, must of course be considered characteristic of the Nearctic 

 area, and might indeed be appropriately added to the 23 or 24 

 genera which are peculiar thereto ; but if this be done, the number of 

 peculiar and characteristic genera taken together reaches only 51 — 

 a smaller number than that of the genera of Land-birds alone (57) 

 which are common to the Nearctic and Palfearctic areas, and con- 

 siderably less than half the number of all genera Avhich are found 

 on both, Avhile that of the remaining genera which are common to 

 the Nearctic area and the Neotropical Region is much larger again, 

 being 151. Again, the total of peculiar and characteiistic Nearctic 

 genera being (as just said) 51, cannot compare with the 264 (or 

 pei"haps more) genera which are peculiar to the Neotropical Region ; 

 while no one can pretend that among the former are there any 

 types of such significance as the latter abundantly aftbrd. Thus 

 regarded from every ornithological aspect, Avhat has been called 

 the Nearctic " Region " has no right to be so accounted, since its 



^ Of these 2 belong to Turdidee, 1 to Chameeidai, Paridse, Troglodytidss 

 respectivelj^, 5 to Erriberizidee, 2 to Corvidse, 1 to each of Picidsz, Falconidsz, 

 and Colimibidie, 5 to Tetraomdee, and 1 to Scolopaeidx, Anatidse, and Laridse 

 respectively. 



