1897] THE PROBLEMS OF BRITISH FAUNA 381 



imd slugs did not invade Ireland until after the Siberian mammals 

 were in England, why were the latter unable to reach Ireland as 

 well? Such, briefly, is Dr ScharfFs argument for the pre-Glacial 

 immigration of the Irish fauna. 



Turning to the Northern section of the fauna, Dr Scharff argues 

 that it must have entered Scotland by a land-connection from Scan- 

 dinavia,, ami so passed southwards into Ireland. This land-connec- 

 tion he believes, in common witli most geologists, to have been 

 ■continued northwards to Spitsbergen, and westward to Greenland 

 and North America. Thus a way was open for animals with a 

 circumpolar range to wander southwards, while North American 

 forms were able to invade Western Europe. The continuous coast- 

 line to the north of the Atlantic, shutting off that ocean from the 

 Arctic Sea, must have ensured a mild climate to its waters and 

 shores. The vast majority of geologists would, of course, regard this 

 land-connection and the migrations which passed over it as post- 

 glacial. Dr Scharff, necessarily considering the northern fauna 

 older than the Siberian, believes, on the contrary, that its entry into 

 our area must be put back to the time when the ice-laden sea of the 

 Lower Boulder Clay covered Central Europe and the newer crags were 

 being laid down in eastern England. The land-connection between 

 Scandinavia and Ireland he considers, however, to have persisted 

 into late Pleistocene times. 



It has already been mentioned that the bulk of the Irish fauna 

 is supposed by Dr Scharff to have come from South-western and 

 South-central Europe, and that the more western section is regarded 

 by him (as the corresponding section of the flora was regarded by 

 Forbes) as the oldest section of the whole British fauna. Dr Scharff 

 does not share Forbes' view of an extensive Atlantic continent ; he 

 believes that a western continental coast-line, including, of course, 

 .a tract to the west of the present British and Irish area, meets all 

 the requirements of the facts. Across the valleys which occupied 

 the present beds of the English and St George's Channels the animals 

 of these southern migrations passed into Great Britain and Ireland ; 

 .according to Dr Scharff, through the Pliocene and up to the earliest 

 Pleistocene period. But the land-connection between Great Britain 

 and Ireland broke down in the south sooner than in the north, so 

 that the arctic migration could go on after the southern migrations 

 had been cut off. Some of the animals of the ' South-central ' 

 migration are traced by Dr Scharff back to Siberia, where he believes 

 they originated. He points out, moreover, that the same species 

 •can sometimes be proved to have taken part both in the ' South- 

 central ' and in the (later) true ' Siberian ' migration. In such 

 cases, however, a distinct race of the species usually characterises 

 each migration. For example, the Irish race of the Pied Deer is the 



