INTRODUCTION. 





As regards its Bird-life the Neotropical Region, which, according to 

 the arrangement usually adopted, consists of America south of the 

 Isthmus of Tehuantepec together with the West Indies*, may be most 

 conveniently divided into six Subregions. These are : 



1. The Transpanamic Subregion, embracing the great Central-American 

 Isthmus from Tehuantepec down to Panama. 



2. The Antillean Subregion, containing the West-India Islands. 



3. The Colombian Subregion, containing the South-American littoral 

 and the adjacent Andean ranges in Venezuela, Colombia, Ecuador, Peru, 

 and Bolivia. 



4. The Amazonian Subregion, containing Guiana and the valleys of 

 the Orinoco and Amazons and their confluents. 



5. The Brazilian Subregion , containing the great wooded and campos 

 districts of Southern Brazil and Paraguay. 



6. The Patagonian Subregion, consisting of Antarctic America up to 

 the Brazilian wood-districts and the highlands of Bolivia on the eastern 

 side of the Andes, and apparently extending as far as the Gulf of 

 Guayaquil on the west. 



It is, of course, impossible to draw a precise line between these six 

 Subregions, and any boundaries assigned to them can only be regarded 

 as approximative ; but it is obvious that nearly, if not quite, the whole of 

 the Argentine Republic, the Avifauna of which we are now considering, 

 comes within the limits of the Patagonian Subregion. It is possible 

 that the birds of the Territory of Misiones and of some parts of Northern 

 Corrientes may be more nearly akin to those of Brazil, but we may say 

 generally that the Argentine Republic belongs to the Patagonian Sub- 

 region. 



* Cf. Sclater, Journ. Linn. Soc., Zool. ii. p. 1J3 (1857). 

 VOL. I. b 



