106 Annals of the Carnegie Museum. 



only in extent, but also in number of species; notwithstanding, their 

 fauna shows a. remarkable amount of specialization. None of the 

 Temperate Zone forms in this particular region show clear indica- 

 tions of having been derived directly from Subtropical forms living 

 immediately below them, but the great majority of the species in both 

 Temperate and Paramo Zones, showing as they do unquestioned af- 

 finities with allies in the Venezuelan Andes, seem to have reached the 

 region over precisely the same course as the fauna of the Subtropical 

 Zone. We concliide, -therefore, that the mountain system over which 

 they passed could not have had an elevation of less than ii,ooo or pos- 

 sibly 13,000 feet. It likewise follows that they have been isolated for 

 a longer period of time than the Subtropical Zone forms. 



Our studies of the avifauna of this restricted region have thus led 

 us to certain general conclusions which may, we think, fairly be al- 

 lowed to stand on the basis of the evidence presented. We find, in 

 brief, that the bird-life of the Santa Marta region has in the main 

 been derived from the east, under peninsular conditions, while there 

 has been a more recent infusion of lowland forms from the west and 

 • south under present topographic conditions. We see further that an 

 imposing mountain chain, comparable to the ■ Andes in height even 

 if not in extent, must once have stretched along the northern coast of 

 the South American continent, in part where the waters of the Carib- 

 bean Sea now roll, serving as a pathway over which many Subtrop- 

 ical and alticoline forms have traveled to reach their present stations 

 in its terminal remnant. From the circumstance that so many of 

 these forms show evidence of having been derived indirectly from 

 Andean antecedents we may, with somewhat less confidence perhaps, 

 postulate a more southern, possibly equatorial, center or centers of 

 origin and dispersion for the life of the Subtropical Zone in general. 

 In all we see that, however complex the immediate problem may ap- 

 pear to be, and however diificult its solution, the diffusion of organic 

 forms over the surface of the earth has not been haphazard, but has 

 proceeded under the operation of certain fixed laws and principles, the 

 discovery and formulation of which are the province of Zoogeographi- 

 cal Science. 



List of Localities. 

 The construction of a suitable base-map on which to plot the life- 

 zones of the Santa Marta region has involved serious difficulties. 



