ScHAUFF — On the Origin of the Enr02)ean Fauna. 451 



Siberian faiina must have taken place dining tlie post-Tertiary (Pleis- 

 tocene) Epoch. " We have evidence," he says (p. 472), " that at the 

 beginning of that epoch, the Arctic Sea extended further south than it 

 does now in I^orth --vrestern Siberia, and that throughout the country 

 the climate "was moister, though this only led to isolated and unim- 

 portant giaciation in the mountainous regions." 



After a careful study of the geological data collected on the 

 mainland and the jSTew Siberian Islands, Tcherski finally concludes, 

 (p. 474) that the southward retreat of the ISTorth -Asiatic fauna was 

 continued, though very slowly, throughout the Pleistocene Epoch 

 without breaks or fluctuations, even duiing the time of the most 

 important glacial developments in Europe. At last the frosts gradually 

 penetrated the soil, and the former haunts of the large Ungulates 

 were then probably only visited during tlie summer migrations. In 

 exceptional cases the carcases of mammoths, musk oxen, and other- 

 animals were preserved in the frozen soil of these northern latitudes 

 to the present day, and there, what are now Arctic species, had 

 undoubtedly lived together with those of southern origin. 



Yery similar views were held by Brandt, who was j)robably the 

 highest authority on the Siberian fauna. He was of opinion (12, 

 p. 249) that the northern half of Asia was inhabited already in Tertiary 

 times by the present fauna, with the addition of several species now- 

 extinct, and that Europe and Asia subsequently underwent a change 

 of climate. In consequence of the increasing cold the vegetation 

 of ]S"orthern Asia suffered severely, and both plants and animals 

 migrated during the Glacial Period towards the south and west, 

 where they found more genial conditions. 



Against these views of Tcherski and Brandt, it might be urged 

 that, as certainly the bone beds in the Liakov Islands (^New Siberian 

 Islands) rest upon a solid layer of ice of nearly seventy feet thick, 

 the Mammals must have migrated north after the amelioration of the 

 Arctic climate which prevailed there during the formation of this ice. 

 Asa rule, however, these layers of ice contain seams of mud and sand,, 

 and it has been suggested by Dr. Bunge, who visited tlie Xew Siberian. 

 Islands recently at the instance of the Imperial Academy of St. 

 Petersburg, that the ice has formed, and is still forming, in fissures 

 of the earth (15). To look upon these so-called glaciers as fossil 

 ice, and as having survived from the Glacial Period to the present 

 day, is a view which, therefore, lacks confirmation. 



During the earlier part of the Pleistocene Epoch iu Siberia there 

 occurred a marine transgression in North-western Siberia, and to judge- 



