388 THE AGE OF MAMMALS 



epochs. Since the mammaUan hfe of the third and fourth glaciations (Riss, 

 Wiirm), according to Penck, is identical in Switzerland at least, we may 

 ascribe tundra, or barren ground conditions, both to the fauna and flora of these 

 final glacial epochs. From the beginning of the last interglacial interval to 

 the present time the vegetation of the region near the Alps has apparently 

 gone through a cycle of changes such as the following : 



Vegetation Climate Period 



4th. Forest West-European, oceanic Modern 



3d. Steppe Southeast-European, continental Post glacial 



2d. Tundra Northeast-European, sub-Arctic Glacial 



1st Forest West-European, oceanic Interglacial 



The steppe and tundra biotic period, according to all authorities, was the 

 great feature of the last glacial phases. 



J^feumayr estimated that the general lowering of temperature of Europe 

 had not amounted to more than 6° C, and believes that even during the Ice 

 Age a comparatively mild climate prevailed in Great Britain. Martins esti- 

 mated that a lowering to the extent of 4° C. would bring the glaciers of 

 Chamounix down to the level of the plain of Geneva. Penck estimates that, 

 all other atmospheric conditions remaining the same as now, a fall of tem- 

 perature to the extent of 4 to 5° C. would be sufficient to give us back the 

 Glacial Period. 



Secular Northward and Southward Migrations of Faunas 



The passing from the Phocene to the Pleistocene is clearly outhned on 

 the east coast of England in Norfolk. After the first great cold wave the 

 life of Great Britain is considerably altered; it constitutes the first fauna, 

 as briefly defined above. This is followed in Europe by the second, by 

 the third, and by the fourth faunas, as more clearly distinguished in the 

 accompanying table, and explained above, p. 375. 



The principal contributors to the theory of northward and southward 

 migrations and to the succession of faunas are Nehring, Woldrich (1882), 

 and more recently Penck. In considering the distribution and migration 

 of the mammals throughout the Glacial Period, we must constantly keep 

 in mind the differences of latitude. Italy had a more moderate climate 

 than central Europe; the reindeer seems never to have found its way there, 

 yet a lowering of temperature in Italy is indicated by the fact that the 

 alpine mammals, such as the marmot (Marmota) , chamois (Rupicapra) , and 

 steinbok (Ibex) came doAvn to the plains.^ The hippopotamus undoubtedly 

 remained in Italy longer than it did in northern Europe, so it is not surpris- 

 ing to find its remains associated with those of the big-nosed rhinoceros (D. 

 merckii) in a cave near Mentone in the French Riviera, which belongs in 



1 Issel, A., Liguria geologie e preistorica. Ref. by Boule in L'AnthropoL, 1893, pp. 602-604. 



