Todd-Carriker: Birds of Santa Marta Region, Colombia. 91 



and affinities of the Subtropical Zone as it is represented in the Sierra 

 Nevada de Santa Marta. It is well specialized, containing no less 

 than thirty-nine autochthonous or peculiar forms, of which twenty are 

 entitled to rank as species. Thus it may properly be considered to con- 

 stitute a distinct Fauna, for which we propose the name Sierra 

 Nevadan. This degree of specialization, taken in connection with its 

 obviously depauperate character as compared with neighboring regions 

 (to which attention has already been called), implies either that its 

 constituent elements have been developed independently, and have al- 

 ways been isolated from their congeners, or else that the region to 

 which they are now confined marks the extremity of their former 

 range, the continuity of which has been interrupted. In the one case 

 the Subtropical fauna would be entirely autochthonous, similar forms 

 ( where such occur) having been developed by parallelism, while in 

 the other case the fauna would be derivative, and due to latitudinal 

 extension of range, followed in many cases by modification as the in- 

 direct result of subsequent isolation. It is quite possible that such 

 distinct forms as Pyrrhura viridiedta, Helianthea phalcrata, Automolus 

 rufipectus, Grallaria bangsi, and Atlapetes melanocephalus may have 

 arisen in the former way, but if so, we are unable to indicate with any 

 degree of certainty their Tropical Zone antecedents, if, indeed, these 

 are still extant. 



Although the Subtropical Zone of the Sierra Nevada is separated 

 from that of the Eastern Andes (at its northern extremity) by a dis- 

 tance of less than twenty miles, there are only four species which 

 are common to the two ranges but not found elsewhere, and only three 

 which have representative forms in these two ranges alone. As al- 

 ready intimated, there are grounds for suspecting that some, if not 

 all, of these cases will be relegated to a different category when the 

 Venezuelan Andes shall have been more thoroughly explored. In any 

 event it is obvious that the Subtropical fauna of the Sierra Nevada, 

 considered as a whole, has practically nothing to do with that of the 

 Eastern Andes, and could not have been derived therefrom directly. 

 It is true that the two ranges have numerous forms in common, but 

 with the few exceptions above noted (and which may not be valid) 

 these are forms of more general distribution, and without especial 

 significance in this connection. The zoological evidence is thus fully 

 in accord -with the geological evidence, and we may confidently assert 



