132 Bulletin American Museum of Natural History. [Vol. XXXVI, 



Thamnophilus canadensis pulchellus Heleodytes nuchalis nuchalis 

 Microrhopias grisea intermedia " zonatus brevirostris 



Furnarius agnatus Troglodytes musculus atopus 



Synallaxis cinnamomea fuscifrons Mimus gUvus columbianus 



" candei candei Thraupis glaucocolpa 



Empidochanes cabanisi Ccereba luteola luteola 

 Heleodytes minor bicolor 



The Orinocan Fauna. — In our work at Buena Vista and Villavicencio, 

 as well as at Florencia and La Morelia, we merely touched the western 

 margin of a major faunal region which reaches to the eastern border of the 

 continent. To define its minor divisions, even were data at hand, would 

 take us far beyond the limits of our subject. It will, however, answer our 

 present purpose to apply, at least provisionally, the term Orinocan Fauna 

 to that part of this region with which we are concerned and restrict our 

 comparison of its life to that of the contiguous areas here under review. 



As has been stated elsewhere (see Expedition No. 7), the llanos or 

 plains of the Meta, at Villavicencio, come directly to the base of the Andes. 

 They bear no large forested areas, but the banks of streams are sometimes 

 wooded, and where the streams overflow there are usually patches of forest 

 growth. But the slopes of the outermost ridge of the Andes are heavily 

 forested from base to summit. 



Our collecting about Villavicencio, was done in the open fields and in 

 the strips of woodland. At Buena Vista, some 3000 feet higher, we col- 

 lected only in the forests and about their borders. Nevertheless there was 

 a surprising similarity in the arboreal tropical bird-life of these apparently 

 quite different localities. Thus, of one hundred and fifty species (chiefly 

 Passeres), forty-eight were found only at Buena Vista, fifty-eight only at 

 Villavicencio, while fifty were common to both places. 



The Amazonian element is apparently quite as strongly shown at Vil- 

 lavicencio as at Buena Vista; twenty-three Amazonian forms collected by 

 Miller at La Morelia and Florencia, being also taken about Villavicencio, 

 and eighteen at Buena Vista. It seems obvious, therefore, that the life of 

 these two localities as it is represented in our collections, may be treated 

 collectively. 



Compared with that of the Amazonian Fauna of southeastern Colombia, 

 it contains a much smaller number of pure Amazonian forms, and much 

 larger number of wide-ranging species characteristic of the arid and semi- 

 arid portions of northern South America. There are also several so-called 

 Guianan species which have not as yet been recorded from upper Amazonia. 

 Indicating doubtless a lower humidity, several species common to both the 

 Florencia and Villavicencio districts are represented at the last-named 



