INTRODUCTION. 3 



should perhaps never have known that, formerly, it 

 must have inhabited that country as well. Of other 

 mammals we possess fossil and also historical evi- 

 dence of their having once lived in these islands. 

 Such are the Wolf and the Wild Boar, both of which 

 were abundant in Great Britain and Ireland. The 

 latter is a distinctly southern species. We assume 

 this, because its remains have never been found in 

 high northern latitudes ; nor does it now occur in 

 Northern Europe or Northern Asia, whilst all its 

 nearest relatives live in sub-tropical or tropical 

 climates. The Arctic Hare, on the contrary, has 

 probably come to us from the north. Its remains 

 are unknown even in Southern Europe, and the 

 more we approach the Arctic Regions, the more 

 abundant it becomes. Thus we have here two 

 instances of British mammals, one of which, the 

 Wild Boar, has died out as it were in a southerly 

 direction ; whilst the other, the Arctic Hare, is ap- 

 parently retreating towards the north. 



There are also some British mammals of which we 

 have no fossil history, at least of which no remains 

 have as yet been found in these islands. Such a 

 one is the Harvest Mouse (Mus minutus). It has 

 a somewhat restricted range in England, and only 

 just crosses the Scottish border in the east. From 

 the rest of Scotland and from the whole of Ireland 

 it is absent. To judge from this distribution, in 

 connection with the fact of its being unknown as a 

 British fossil species, it is probably a late immigrant 



