Todd-Carriker: Birds of Santa AIarta Region, Colombia. 101 



assuming that the east and west trend of the range would have had 

 the same effect in lowering the life-zones throughout its length as is 

 the case at present in the Sierra Nevada. But here another factor, gla- 



Fig. 9. Range of Oxypogon, a genus of the Paramo Zone, to illustrate the 

 breaking up of the group into distinct species in the several parts of its range. 

 (1) O. stuebelii; (2) O. guerinii ; (3) 0. lindenii ; (4) O. cyanolarmus. 



ciation, may have come into play. It is very probable that during the 

 Pleistocene the snow-line may have stood at a somewhat lower level 

 than today, and this would naturally have had the effect of lowering 



