320 



Annals of the Carnegie Museum. 



when on the same side of the continental divide, because conditions 

 of humidity are so different on the Pacific slope from those on the 

 Caribbean. While the slope is much more gradual on the western 

 side than on the eastern, the humidity is so much lower, that no 

 rational comparison can be made. 



Taking into consideration all of these factors, we may make the 

 following classification of the life-zones and give some of the species 

 most characteristic of each. 



Primary Areas. Regions. Zones or Belts. Altitude (Feet). 



Boreal Boreal Canadian io, ooo to 1 1 ,000 



Sonoran. 



Tropical. 



Upper Sonoran 

 Lower Sonoran 



Sub-Timberline 8,000 to 10,000 



Upper Plateau 5, 000 to 8,000 



Lower Plateau 2,500 to 5,000 



Plains Region 100 to 2,500 



Tropic o to 1,500 



Sub-Tropic 1,500104,000 



Humid -< 



Cordilleran 4,000 to 7,000 



^Sub-Andean 7,000 to 10,000 



North Coastal o to 1,200 



South Coastal o to 1,200 



Foot Hills 1,200 to 4,000 



Cordilleran 4,000 to 7,000 



Sub-Andean (extralimital) 



Semi-Arid -< 



^ Arid (extralimital ) 



Canadian Zone (10,000 to 11,000 feet). 



The only portion of Costa Rica which we can class under this head 

 is the region above timber-line on the high volcanoes. Here in this 

 bleak, cool region, where the only vegetation consists of scrubby 

 bushes and shrubs, lives the sole remnant of the Canadian fauna, 

 Junco vulcani. 



Sub-Timberline Belt (8, ooo to 10,000 feet). 



Between the altitudes of about 8,000 and to, 000 feet lies a belt of 

 hard-wood forest containing many oaks and other trees characteristic 

 of the more northern arboreal flora. These trees are not tall, are more 

 or less spreading, and toward the upper portion of the zone become 

 stunted and gnarled from the low temperature and high winds often 

 prevailing. In this belt are found numerous characteristic species 

 which seldom go below it. On the higher peaks it does not extend 

 so low as on some of the lower ranges, for example on the volcanoes 



