340 THE HOLARCTIC REGION. [CHAP. 



aid of the borer, but their evidence is, nevertheless, unimpeach- 

 able. 



From these and other lines of evidence, we learn that during 

 the Plistocene epoch not only was England connected with France 

 across the English Channel, but that the land extended up the 

 North Sea at least as far as the Dogger Bank ; the Ouse, the 

 Thames, the Rhine, and perhaps the Elbe originally uniting to 

 form one mighty river, discharging far up in the North Sea. 

 During a portion of this period Ireland was in connection with 

 the British Islands; and it has been suggested by Leith- Adams 1 

 that the connection was with Scotland, owing to the circumstance 

 that, with the exception of the cave-bear, all the living and extinct 

 Irish mammals have been recorded from Scotland, while a number 

 of the English Plistocene mammals appear never to have reached 

 the latter country. On the other hand, Dr R. F. Scharff 2 , from a 

 study of the freshwater fishes and molluscs, is of opinion that 

 " Ireland was in later Tertiary times connected with Wales in the 

 south and Scotland in the north ; whilst a freshwater lake occupied 

 the present central area of the Irish Sea. The southern connec- 

 tion broke down at the beginning of the Plistocene period, the 

 northern connection following soon after. There is no evidence 

 of any subsequent land-connection between Great Britain and 

 Ireland." Since the above was written Dr Scharff (Mem. Soc. 

 ZooL France, vol. vin. pp. 436-474, 1895) has further developed 

 his views on the origin of the Irish fauna. He concludes that 

 all the Irish mammals reached the island in the early Plistocene 

 (Forest-bed); such British forms as are unknown in Ireland being 

 considered to have reached Britain later, when Ireland was 

 isolated. 



Further reference to the former connection or connections 

 between Britain and the Continent will come more conveniently 

 later. 



The generic and specific mammalian types common to the 

 eastern and western divisions of the Holarctic region 



Western 



Division of the having been already referred to, we may at once 

 proceed to the consideration of those characteristic 



1 Proc. Roy. Irish Acad. Ser. 2, Vol. III. (1883). 



2 Appendix, No. 25. 



