17 12 Proceedings of the Royal Irish Academy. 



various peculiar Scottish forms of archaic or Norwegian relationship which are 

 found isolated in islands in several parts of the area suggest a wide expanse of 

 land of ancient duration stretching from the outer Hebrides to Skandinavia, 

 but not including Shetland; in fact, they form the oldest part of the British 

 fauna. Here, if at any place north of the Thames valley, survivals of the pre- 

 glacial fauna seem to have been possible, and may thus account for the presence 

 of the Orkney Mice, the ancestor of which, M. ewneri, accompanied those of 

 the Skoiner Mouse in the late Pleistocene of Ightham, and are represented 

 to-day by M. sarnius in the Channel Islands. It may possibly account for 

 the " Exiled " Vole-mouse of the Outer Hebrides, M. agrestis exsul, which has 

 its nearest ally in Skandinavia, as well as for the close relationship of Lepus 

 timid us of Skandinavia with L. timiclv.s seoticus of Scotland. 1 



A study of the late English pleistocene mammals shows that the process 

 of extinction was not confined to Ireland. For instance, of eight mierotines 

 found fossil at Ightham, not a single form is now living on the same ground. 

 More than one are quite extinct, and the remainder are dispersed far and 

 wide, a striking testimony to the severity of the Glacial Epoch, and also a 

 reminder to us that the fact of a species having been found in any particular 

 deposit within the area of its modern distribution is no proof that it has 

 existed on those grounds throughout the intervening period. Nothing is 

 more certain than that with the changing of environments species and whole 

 faunas must have waxed, waned, and vanished, to reappear in new forms 

 and conditions on the return of more favourable environments. 



Summary. 



There are no indications that the Mammal-fauna of Clare Island is 

 ancient as compared with that of Ireland, or that the island itself has 

 long been severed from the mainland. 



The earliest known Irish mammals belong to a late pleistocene horizon 

 corresponding to that of Ightham fissure, Kent, but much poorer. This poverty 

 probably indicates imperfect knowledge. 



The members of this fauna became extinct in Ireland, probably in 

 consequence of a recent Glacial Period. 



The present fauna is, with the exception of the peculiar Stoat, an im- 

 poverished edition of that of southern England from which it was derived, 

 and not from that of continental Europe or Scotland. It could not therefore, 

 as a whole, have survived the Glacial Period in Ireland, and it is suggested 



1 There may also be in Noway a second form of L. timidus, the relationships and status of which 

 have not vet been mode clear. 



