The Scottish Naturalist. 55 



forth by Mr Alston are several, but I do not think that they 

 will tell very much against his general conclusions. It is more 

 than doubtful that the emigration into Ireland of the Scottish 

 mammals took place between south-west Scotland and north- 

 east Ireland, because, though the Irish Sea was absent, a great 

 lake, "averaging 25 miles at least in breadth," stretched from 

 the head of the Sound of Jura to Wales, and would present 

 an effectual obstacle to the passage of the majority of the 

 mammals. That Ireland derived many members of its fauna 

 from Scotland seems clear ; but before getting to Ireland, they 

 would have to come farther north in Scotland than Mr Alston 

 supposes. 



It also seems very doubtful whether the Irish Deer (Mega- 

 ceros giganteus) reached Ireland by way of Scotland, in which 

 it seems to have been of very rare occurrence, though abound- 

 ing in Ireland and the Isle of Man. " It may quite well," says 

 Dr James Geikie, 1 "have entered Ireland from the south, 

 crossing the river that flowed south through St George's Channel." 

 Satisfactory evidence is yet wanting that either the Irish Deer 

 or the Mammoth revisited Scotland after the close of the glacial 

 epoch, though they were certainly to be found in other parts of 

 the British Isles. The Reindeer, on the other hand, was certainly 

 a postglacial (as well as an interglacial) animal in Scotland. 

 Mr Alston's first category seems, therefore, to require emenda- 

 tion. Though from the scarcity in Scotland of interglacial 

 deposits (these having been swept away by the last ice-sheet) 

 it is impossible to say what species came to it during the 

 genial interglacial periods, it is tolerably certain that it had 

 many mammalian inhabitants, including, perhaps, many of still 

 existent species, and others long since extinct in Britain. The 

 first category would therefore include many more species than 

 the two mentioned above. Amongst these we know for certain 

 was the Irish Deer. But all these animals would be driven 

 out of Scotland by the last ice-sheet, and the colonisation would 

 would have to be done over again. In the second category 

 would therefore have to be included the Reindeer, and, more 

 doubtfully, the Irish Deer and Mammoth. As for the other 

 animals mentioned in this and the remaining categories, they 

 may have arrived in the order that Mr Alston assigns to 

 them ; and he has certainly brought forward suggestive evidence 

 in favour -of his views. On the other hand, the eastern side 



1 Prehistoric Europe, p. 512. 



