PLEISTOCENE OF EUROPE, NORTH AFRICA, AND NORTH AMERICA 415 



As indicated in the repetition in the above columns, the mammals are 

 not all closely confined to these life zones; but certain of them, especially 

 the elephants, bison, reindeer, the rhinoceroses, and 'probably the primitive 

 cattle and arctic hare, wandered freely and had a wide range. Other forms, 

 like the nuisk ox, jerboa, the saiga antelope, the moos(% are each respec- 

 tively distinctive of the tundra, steppe, or forest environment. 



Tundra Jawia and flora. — Animals like the lemming ^ {My odes torquatus), 

 adai)ted to extreme conditions, generally cling to these very obstinately, and 

 perish rather than conform to altered environment. This animal dwells 

 immediately to the north of the region of coniferous forests, among scattered 

 shrubs of the common juniper {Jimiperus communis) and the; dwarf birch 

 {Betula nana). Thus we may be perfectly certain that the lemmings dis- 

 covered in England, France, Belgium, and a large part of Germany in Pleis- 

 tocene times are proofs of conditions which prevailed, similar to those of 

 the present circumpolar region. The lemmings probably advanced south 

 with the characteristic tundra fauna, and we must conclude that there were 

 tundras in central and western Europe for a time during the Pleistocene. 

 At Thiede near Braunschweig, the classical locality for lemming, the re- 

 mains are associated solely with those of the arctic fox, arctic hare, reindeer, 

 musk ox, and mammoth; thus a comparison of northern Eurasia and the 

 'barren grounds' of northern Asia and North America is quite justifiable. 

 Characteristic plants of the period are the dwarf birch (Betula nana), polar 

 willow {Salix polaris), mountain dryas (Dryas odopetala). The lemmings 

 probably dwelt in the immediate neighborhood of the glaciers. As the 

 climate grew warmer they retreated with the tundra fauna to the north, the 

 high grassy slopes of the mountain sides being the last to be deserted. The 

 arctic hare (Lepus variabilis) in the British Isles is now confined to Ireland 

 and the mountains of Scotland. 



As the lemming is typical of the tundras, the jerboa (Alactaga) is typical 

 of steppe conditions; thus the succession of three rodents indicates approxi- 

 mately the succession of tundra, steppe, and forest conditions, as follows: 



Tundra, the lemming (Myodes torquatus) 

 Steppe, the jerboa (Alactaga jaculus) 

 Forest, the squirrel (Sciurus vulgaris) 



Steppe fauna. — This fauna in deposits at several different points is 

 definitely proved to have followed the tundra fauna. Both Nehring ' and 

 Woldrich '' hold that the steppes of central Europe were post-glacial. Accord- 

 ing to Woldrich (1896) the tundra and steppe types of Europe represent the 



> Nehring, A., tJber Tundren und Steppen der Jetzt- und Vorzeit, mit besonderer Be- 

 riicksichtigung ihrer Fauna. Berlin, 1890, pp. 81-166. 



2 Nehring, op. cit., 1890, p. 222. 



' Woldrich, .1. N., Ueber die Gliederung der anthropologischen Formation.sgruppe Mit- 

 teleuropas. Silzher. kgl. bohm. Ges., math, naturwiss. Classe, 1896. Re/. Maliegka in Central- 

 blait Anthrop., 1896, pp. 142-143. 



