492 Proceedings of the Boi/al Irish Academy. 



presence of northern forms is due, as "vre have seen, to an immigration 

 of Siberian animals ; but, as they lived in company with southern 

 types, many of which required an abundance of green food, the 

 winter temperature in the British Islands may have been as high or 

 higher than it is now, though with a lower summer temperature, and 

 with a copious snow-fall in winter, glaciers were generated in the 

 mountainous regions. A number of land and freshwater shells are 

 quoted by Prof. J. Geikie (35 a, p. 337), from the Arctic freshwater 

 bed on the coast of Norfolk, in evidence of a rigorous climate. These 

 are spoken of by him as high northern forms ; but in this he is 

 mistaken. Every one of them are inhabitants of Ireland at present^ 

 and all but one very common. 



But if the fauna does not indicate Arctic conditions during the 

 Pleistocene Epoch in the British Islands, we are told that what is 

 known of the flora, at any rate, is such as to exclude the possibility 

 of its existing under anything but an Aictic climate. The same 

 Arctic freshwater bed just referred to contains, besides the shells, 

 some plant-remains, and these, according to Mr. C. Eeid, imply a 

 lowering of the temperature by about 20- F. The plants of the Eorest- 

 bed, Mr. Clement Eeid tells us [12a, p. 186), are not Arctic. Though 

 the land and freshwater molluscan fauna remains much the same in 

 the later deposits, the plants alone, it appears, are quoted as indica- 

 tors of temperature. Prof. Xathorst has made the Pleistocene flora 

 the subject of his special study, and to his writings we must appeal 

 for information on this subject. It appears, from his interesting essay 

 on the distribution of the Arctic plants in Europe during the Glacial 

 Period (61 h), that all the localities but one, in which remains of such 

 vegetation have been discovered, lie either within the limits of the 

 maximum extension of what is known as the northern ice-sheet, 

 or within those of the Alpine glaciers. It is conceivable, therefore, 

 that the remains of the vegetation in question were carried down 

 from the mountains by glaciers, and deposited far from where they 

 originally flourished. Such a transportation from a distance is still 

 more easily conceived when we consider that, as has been suggested, 

 the limits of the maximum extension of the Scandina-vian ice-sheet 

 merely represent the shores of a Xorth European sea, and that the 

 plants, along with the boulders, have been left by stranded icebergs, 

 where we now find them. The Arctic willow {Salix 2JoIari8) and the 

 dwarf birch 'Betida nana], which occur in the so-called Arctic fresh- 

 water beds of Norfolk, might have reached their destination from 

 Scandinavia in that manner, without influencing the British climate 



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