144 SCLATER ON THE GENERAL DISTRIBUTION OF AVES.' 



nearly the whole of them belong to tropical America, a few species 

 only ranging into the northern portions of that continent. It is 

 of course quite impossible to ascertain exactly the boundary be- 

 tween the northern and southern zoological regions of the New 

 "World ; but many of the peculiar forms of the southern division 

 appear to extend some way up the coast-line of Southern Mexico, 

 even north of the isthmus of Tehuantepec ; whilst northern forms 

 range down the table-land quite into the Southern States of the 

 Mexican Union. Thus we find one or two representatives of all 

 the most characteristic South American groups occurring to the 

 north of Panama, — Galbula melcmogenia representing the Galhu- 

 lidcB ; JPipra mentalis and Manacus Candcei, the PiprincB ; Calliste 

 larvata, the genus Calliste ; Cotinga amabilis, the Cotinga, and so on. 



The Antilles seem to be a kind of debateable ground between 

 the two regions, but are more properly referable, I suppose, or at 

 least the greater portion of them, to the southern region. They 

 furnish us, however, with several peculiar genera which do not 

 occur elsewhere. 



The Neotropical Eegion is without doubt, I think, rich in number 

 of species beyond any other. A calculation which I made some 

 short time ago of species occurring southwards of Panama gave 

 me — 



1 . Accipitres 95->^ 



2. Passeres 1360 



3. Scansores 230 



4. Columbffi 25 



5. GaUinffi 80 



6. Struthiones 2 



7. Grallse 128 



8. Anseres 80 



V2000 species j 



J 



and I am decidedly of opinion that, what with taking recent addi- 

 tions into consideration and adding on Central America, we can- 

 not estimate the number of birds belonging to this region at less 

 than 2250. Taking the approximate area at 5| millions of square 

 miles, this will give a species to each 2400 square miles. It fol- 

 lows, therefore, that this region is more richly endowed with 

 ornithic species than any other portion of the globe. 



