GEOGRAPHICAL DISTRIBUTION 325 



river whence it has its name, but the peculiarities of the lower 

 portion not being observable in the higher tributaries of that 

 mighty flood, its upper waters must be regarded as draining land 

 that belongs to another Subregion, which, intervening between the 

 Patagonian and first the Brazilian and next the Amazonian, in- 

 cludes all that is left of South America, and has been named the 

 " Subandean." To this also belong on the one side the Galapagos 

 — ever memorable as the place where, as Darwin has told us, there 

 first dawned on him, from a consideration of their Birds, the 

 doctrine of Natural Selection, which has led to such fruitful and 

 stupendous results— and on the other side Trinidad and Tobago, 

 beside the islands on the northern coast of South America. This Sub- 

 region reaches the " Central American " in the Isthmus of Panama, 

 and of the limits of this last none can yet speak with certainty.^ 



The difficulty of distinguishing these Subregions is very great, 

 and the close alliance between all but the Patagonian and Antillean 

 will be plain to any one who analyzes the differences as shewn by 

 the prevalence in them of the various Families of Birds peculiar 

 to the whole Region.^ That the most characteristic features are 

 exhibited by the Patagonian none can doubt, and indeed therein 

 we find, as might be expected, the nearest resemblance to the 

 Fauna of New Zealand or the Australian Region, and some of the 

 best evidence of the antiquity of its population. These are the 



^ Messrs. Godmau and Salvin, and there can be no better authorities, suscest 

 {Ibis, 1889, p. 242) that the northern limit of certain species of Psittaci " may- 

 be almost said to define the boundary between the Nearctic [Holarctic] and Neo- 

 tropical Regions." They also point out that the same limit is practically that of 

 the Trogonida&, and on the eastern side that of the Momotidsa. It is also the 

 termination of the Cracidse, with the exception of an Ortalis, and of the Tinamidm, 

 while among the Passeres the same boundary confines Pachyrhamphus, one of 

 the Cotingidse, an essentially Neotropical Family, on both sides. " From this it 

 will be seen that the line of demarcation between the two regions, so fir as the 

 birds are concerned, is capable of being defined with some precision, and will be 

 found to coincide with the northern limits of the forests. These on the eastern 

 side leave the coast a little north of Tampico, and continue in a narrow belt along 

 the eastern flank of the mountains in a nearly northern direction almost to 

 Monterey. On the western side a similar state of things is found, and we meet 

 with a number of southern forms extending along the western slope of the 

 mountains as far as Alamos " in Sonora. 



- It is only in deference to Mr. Salvin's views that I do not rank the Subandean, 

 Brazilian, Amazonian, and Central American areas as Provinces, and group them 

 to form a single Subregion. Recognizing of course the Antillean Subregion, I 

 hold the existence of a Patagonian Fauna to be unquestionable, whatever be its 

 geographical limits ; but as regards the rest I am prepared to find that future 

 consideration will justify the suggestion just made, so that the Neotropical 

 Region will be deemed to be composed of three Subregions only, the Antillean, the 

 Patagonian, and one which (comprehending the four areas above named), for 

 want of a better epithet, might perhaps be called the " Columbian." 



