50 NORTH AMERICAN FAUNA. [no. 27. 



ARCTIC ZONE. 



The Arctic zone comprises the islands of the Polar Sea and the 

 area commonly known as the ' Barren Grounds,' stretching across 

 the northern part of the continent north of the great transcontinental 

 coniferous forest. The physical characteristics of the country com- 

 prised in the Arctic zone are given in the description of the Barren 

 Grounds (p. 4G). Various shrubby plants are common, among which 

 Rhododendron lapponicum, Cassiope tetragona, and several dwarf 

 willows are perhaps the most characteristic. Several other less strictly 

 representative plants also are abundant. The zone is further charac- 

 terized by the presence of certain mammals, as the lemmings of the 

 genera Lemmus and Dicrostonyx, the Arctic fox, musk-ox, Barren 

 Ground caribou, and polar hare. The birds which characterize this 

 area are migratory, spending only the breeding season within its 

 boundaries. They comprise, among the Anatidae, the various species 

 of the genus Chen and one or two genera of maritime ducks. Among 

 the Limicolse, the genera Lobipes, Phalaropus, Macrorhamphus, 

 Tringa and related genera, Calidris, Tryngites, Numenius (hudson- 

 icus and borealis), Squatarola, Charadrius, and Arenaria. The Gal- 

 linse are represented by Lagopus lagopus and L. rupestris, the 

 Raptores by the gyrfalcons, and the Passeres by Plectrophenax, Cal- 

 carius lapponicus and C. pictus, and Anthus. 



The southern extension of the Arctic zone, the Arctic-Alpine, 

 occupies the treeless summits of mountains which lie within the 

 forested area. It comprises in this region the summits of the Rocky 

 Mountain Range. The inconsiderable barren areas that occur on 

 the mountains east of the Mackenzie are near the main Barren 

 Ground area and of course have closer affinities with the true Arctic 

 than with the Alpine summits farther south. Since the mountain area 

 west of the Mackenzie is practically unknown geographically, it is 

 impossible to define the limits of the Arctic-Alpine area with even 

 approximate accuracy. On these mountains timber line occurs, on the 

 sixty-second parallel, at an altitude of about 3,000 feet, and at a 

 diminishing altitude to the northward. As the best information 

 available indicates that extensive areas lie above 5,000 feet, the 

 amount of country to be classed as Arctic- Alpine must be very large. 

 Farther south the zone occupies isolated peaks down to or below 

 latitude 35°. 



The Arctic- Alpine zone along the northern Rocky Mountains is 

 characterized by various dwarf willows and several other plants 

 representative of the Arctic. Its mammals are the Dall sheep {Ovis 

 dalli), the pika (Ochotona), and probably the hoary marmot {Mar- 



