OSBORN. REVIEW OF THE PLEL^TOCENE 251 



first appear in Europe, only to be succeeded in the Third Interglacial or 

 Eiss-Wiirm Stage by the reappearance of the warm African-Asiatic fauna, 

 including the straight-tusked elephant {E. antiquus) and tlie broad- 

 nosed rhinoceros {D. merckii). Theoretically this warm fauna was again 

 driven out during the Fourth or Wlirm giaciation by the reappearance of 

 the woolly elephant and the woolly rhinoceros. Penck"^^ observes, as 

 noted above, that we cannot hope to trace a continuous evolution of forms 

 during the Pleistocene because we are not dealing with the development 

 of one successive series in one locality but with the cycical evolution of a 

 number of different faunas compelled to migrate because of alternations 

 of temperature and of flora, the mammals disappearing and ]'Ptnrning at 

 intervals too brief to allow of any marked evolutionary changes. Herein 

 lies our difficulty when we attempt to distinguish between the Tundra 

 Fauna of the Third and Fourth glaciations and the Forest Fauna of the 

 corresponding interglacial stages, because the faunas return not only with 

 the same generic but with the same specific types, as is especially illus- 

 trated in the case of the mammoth {E. primigenius) and the giant deer 

 (Megaceros), 



Resident Theory. — Another theory is j^resented in the accompanying 

 table, namely, that during the First. Second and Third Glacial Stages 

 the climatic conditions of Europe were temperate except in the immediate 

 regions surrounding the glaciers. It was these glacial border regions 

 which attracted the tundra fauna of the north, the reindeer and the 

 woolly mammoth. Supporting this theory is the fact that the tundra and 

 steppe fossils are found only in proximity to the ice caps and glaciated 

 regions. It is not until the Fourth Glacial Stage and the Postglacial that 

 the general climate of Europe was so severe as to cause the gradual emi- 

 gration and extinction of the African-Asiatic fauna. At this stage re- 

 mains of the tundra and steppe mammals occur in all parts of Europe, 

 including the Pyrenees and Cantabrian Alps, but only partly extending 

 into Spain. 



Latitude and Altitude. — In considering the distribution and migration 

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

 in mind the differences of latitude and of climate which prevailed then 

 as now between Italy, Spain, southern and northern France. Germany 

 and Belgium: also the differences of altitude as between the lowlands of 

 the rivers Ehone and Dordogne and the highlands of the Alps and other 

 mountains. Italy had a more moderate climate than central Europe ; the 

 reindeer seems never to have found its way there, yet a lowering of tem- 



^ Penck, a. : "Die alpinen Eiszeitbildungen und der prahistorische Mensch." Arch. 

 Anthropol.. N. S.. Vol. I. No. S. pp. TS-Oo. 1'. ()4. 



