ScHARFF — On the Origin of the European Fauna. 449 



forty species live in the Holarctic region, while only a few enter the 

 boundaries of the adjoining regions. The majority of them are 

 entirely confined to North America and Asia, while none have a very 

 wide range in Europe. But we have also undoubted geological evi- 

 dence from the remains discovered in the Tchernosjem district of 

 Southern Russia, and described by Prof. Nehring (62(?), that a migra- 

 tion on a vast scale must have taken place. And as we proceed 

 westward, we still find in strata of a similar age traces of the same 

 invasion, but in such diminishing numbers of both species and indi- 

 viduals, that there can be no doubt whatsoever as to its direction from 

 east to west. Even at the present day there are occasional recur- 

 rences of these events of past ages, though on a much smaller scale. 

 It is not many years ago that an announcement was made to the 

 naturalists of Western Europe that enormous flocks of Pallas's sand- 

 grouse {Syrrhaptes paradoxus), a native of Central Asia, had suddenly 

 appeared in Eastern Germany. A few weeks later they invaded 

 England, and a good many even came as far as Ireland. 



The accompanying map has been constructed from data furnished 

 by fossil remains of the Siberian fauna, ^ and is intended to show more 

 clearly the direction of the migration throughout Europe in past 

 times. More recently many of the survivors of this migration in 

 Europe have spread into regions to which they had originally no 

 access. Thus many have penetrated into Scotland, Scandinavia, Italy, 

 and the Spanish peninsula long after the bulk of the invasion had 

 either become extinct or had retired to their native home. 



According to the prevalent views of the origin of the Alpine fauna,- 

 tlie more Arctic members of the Siberian invasion should have found 

 a congenial home in the Alps, but they did not survive there any 

 more than in the plains. Such typical Arctic species as we find there, 

 for example the Arctic hare, either originated in the Alps, or migrated 

 to them at a much earlier period (see p. 471). 



"We have still to inquire into the causes which led to the Siberian 



migration, and to ascertain the geological period during which it took 



place. In order to arrive at a more satisfactory conclusion on these 



j)roblems, it is of some moment to study the extinct fauna of Siberia. 



"The Siberian palaeontologist," observes Tcherski (88, p. 487), 



' The distribution of fossil Mammalia has].been compiled from Nehring (62 h), 

 Woldrich (93), Woodward and Sherborn (95), Harle (38). 



- Compare these views with those expressed on this subject by Prof. Th. Studer 

 <82, p. 28). 



