THE FAUNA OF BRITAIN. 121 



to determine the geological age of the different 

 migrations in so far as they affected the British 

 Islands. I may be excused, therefore, for again 

 quoting the following important passage in one of 

 his works. " The absence," he says (, p. xxix), " of 

 the beaver and the dormouse from Ireland must be 

 due to the existence of some barrier to their westward 

 migration from the adjacent mainland, and the fact 

 that the Alpine hare is indigenous, while the common 

 hare is absent, implies that, so far as relates to the 

 former animal, the barrier did not exist." The Beaver, 

 Dormouse, and Common Hare are either Siberians or 

 later migrants from elsewhere, and there can be no 

 doubt that at the Forest-Bed period Ireland was 

 already, or was just being, separated from England. 

 All the southern species, that is to say all the 

 Lusitanian, Alpine, and Oriental forms occurring in 

 Ireland, must therefore be older than that period. I 

 have advocated similar views in a former essay on 

 this subject. Mr. Carpenter recently advanced some 

 interesting and valuable criticisms on these views, 

 which we may examine a little more closely (p. 385). 

 " While, then," he remarks, " I find myself in almost 

 complete agreement with Dr. Scharff with regard to 

 the older sections of our fauna, I think that those 

 widespread species which survived the Glacial period 

 must have been confined to the more southern parts 

 of our area, and have only subsequently spread 

 northwards and westwards to Scotland and Ireland." 

 He suggests, in fact, that the widespread British 



