Distribution of Birds. 539 



revolutionary change made by commencing the catalogue 

 with the lowest birds instead of the highest, and thus revers- 

 ing the ordinary plan of airangement, was both unnecessary 

 and inconvenient. I may further add that, though I am of 

 opinion that subspecies undoubtedly exist in nature, and 

 although I agree that the best way of designating them is by 

 the use of trinomials, I cannot but think that our American 

 fellow-workers are moving on a little too fast in this matter. 

 Hardly a month now elapses without the receipt in Europe 

 of " advance sheets " and " authors' editions " of papers con- 

 taining descriptions of new subspecies of North-American 

 birds, and it appears to be very questionaVde whether these 

 are always based upon sufficient characters. Even sub- 

 species ouglit to be made practically recognizable. Nearly 

 all species spread over an extensive area vary at their 

 extreme limits from the central form ; but these variations 

 may be so slight as not to necessitate separation even as 

 subspecies. 



The total number of species of birds recognized in the last 

 edition of the 'Check-list,' that of 1889, is 768. We may 

 therefore reckon about 800 species as the limit of the number 

 of those met with in the Nearctic Region, which thus probably 

 has the poorest avifauna, numerically, of all the six primary 

 Regions. 



VI. — The Neotropical Region {Regio Neotropica) . 



(a) Extent. — South America, Central America up to 

 Southern Mexico, and the Antilles. 



(b) Characteristic Forms. — As regards its bird-life, the 

 Neotropical Region is pre-eminently well marked, and has, 

 in fact, a greater number of well-defined families of birds 

 peculiar to it than any of the other five regions. It has also 

 probably a greater number of species met with within its 

 area than any other part of the world's surface. The 

 following 23 families of birds are entirely restricted to the 

 Neotropical Region, and are highly characteristic of its 

 oriiis: — 



