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



geris jugularis, Galbula ruficauda, Myrmeciza longipes^ boucardi, Furnarvus 

 agnatus, Atalatriccus p. pilaris, Hapalocercus meloryphus, Manacus manacus 

 flaveolus, Heleodytes m. hicolor, H. brevirostris, Planesticus a. ephippialis, 

 Saltator maximus, Arremenops conirostris, Thraupis palmarum melanoptera, 

 Cyanocorax affinis, etc. 



To this list others might be added. Doubtless further field work in the 

 Cauca Valley will result in the discovery of some of them, but it seems clear 

 that there will still remain -a goodly number whose absence can be accounted 

 for only by the isolation of the valley. I dwell on the fact for, it seems 

 clearly to indicate that the life of the Cauca was acquired under existing topo- 

 graphic conditions. 



Notwithstanding its nearness to the Pacific coast and the comparatively 

 low altitude of the Western Andes, few species have entered the Cauca 

 Valley from the Pacific coast. This cannot be wholly due to the differences 

 in the physical characteristics of these two districts, since there are many 

 species of the Pacific coast which would find a congenial home in the Cauca 

 Valley, but which have evidently been prevented from entering it by the 

 intervening mountains. 



In the appended list of nineteen species common to the Pacific coast 

 and Cauca Valley, at least thirteen are of East Andean origin, and are more 

 likely to have entered the Cauca Valley from the lower Cauca-Magdalena 

 district than from the Pacific coast. Marila nationi is a duck of unknown 

 origin, Leptotila plumbeiceps occurs as far north as Central America and is 

 doubtless found in the lower Cauca-Magdalena district, where Pachy- 

 rhamphus dorsalis is also found, leaving therefore only two species, Tanagra 

 saturata and Manacus vitellinus iiitellinus which with any certainty can be 

 said to have entered the Cauca Valley from the Pacific coast. 



The life of the Cauca Valley has been therefore derived, with surpris- 

 ingly few exceptions, from that part of South America lying east of the 

 Andes, and has but slight affinity with that of the Pacific- Colombian 

 Fauna. 



But if the Pacific coast has given but little to the life of the Cauca Valley, 

 the valley has made noteworthy contributions to the arid upper Dagua 

 Basin lying in the Tropical Zone on the western slope of the Western Andes. 

 Of thirty-three species taken by Richardson at Caldas on the upper Dagua, 

 sixteen are common to the Pacific coast and the Cauca Valley, thirteen are 

 known from the Cauca Valley but not from the Pacific coast, while only one, 

 Sayornis n. cineracea, is recorded from the Pacific coast but not from the 

 Cauca Valley, where, however, it may occur. This case clearly illustrates 

 the necessity of giving due consideration to suitability of environment in 

 any attempt to solve distributional problems. The Pacific-Colombian 

 Faunal area, an intensely humid district, cannot be expected to enter 



