S. V. Wood, Jun. — The Post- Glacial Period. 157 



themselves as best they could to its adverse influence, until this even- 

 tually brought about their extinction ; the assumption of a hairy coat 

 being merely one of those efforts to protect itself which nature helps 

 animals to make. Doubtless the pachyderms for a long time re- 

 sisted these influences by a southward migration during winter, when 

 their places were taken by the reindeer, which, in its turn retiring 

 northward in the summer, gave place during that season to the 

 pachyderms ; and in this way, probably, their bones have become 

 intermingled in Post-glacial deposits. But this southerly migration 

 of the pachyderms being limited in Europe by the Mediterranean 

 and Black Seas, and in Asia by the great mountain chains that stretch 

 across the centre of that continent, would only afford relief so long 

 as the cold did not necessitate their more southerly retreat. The 

 same kind of problem seems presented to us by North America, 

 where the Tapir,^ found fossil in Carolina, but now confined to the 

 south of the Panama Isthmus, once ranged ; and where the larger 

 felinse, which abound in the southern part of North America, decline 

 to follow their prey into the inclement region of the north. 



Mr, Dawkins has dwelt upon the absence of reindeer remains 

 from those older Post-glacial formations, such as the Brick-earths of 

 the eastern valley of the Thames, and of Clacton, which yield a 

 mammalian fauna with a somewhat older facies than the generality of 

 the Post-glacial deposits,^ and with which fauna the river shell Cyrena 

 flimiinalis occurs in association. He has indeed insisted that the 

 mammalia of these formations indicate an even warmer climate than 

 now prevails in Britain ; ^ and so much was he impressed with this, 

 and with the older facies presented by the remains, that he at first 

 assigned a Pre-glaeial age to the formations in question. This view 

 of their age he has since relinquished,* but, with the exception of 

 the occurrence of some remains of the Musk-ox, the inference he 

 drew as to the warmer climate and older palseontological aspect pre- 

 sented by the group of mammalia yielded by these formations 

 remains, so far as I know, untouched. These formations, I have 

 endeavoured elsewhere to show,' seem to me to have been accumu- 

 lated about that middle stage of the Post-glacial period when condi- 

 tions of climate adequate to produce ice, capable of the transport of 

 blocks, were again coming upon a region that had long enjoyed a 

 temperate climate. If we look at the distribution of the existing 

 species of Elephant, Ehinoceros, and Hippopotamus, we see that their 

 northerly migration into the regions once occupied by their fossil 

 congeners is prevented by the Mediterranean and Black Seas, and by 

 the lofty and snow-capped mountain-ranges which stretch from the 

 Black Sea to the southern frontier of China ; the bridge which Capt. 



^ I omit the Mastodon, as we have no living analogue of that animal wherewith 

 to judge of its climatal peculiarities. 



* Quart. Jouin. Geol. Soc, vol. xxiii., p. 108; vol. xxiv., p. 515; vol. xxv,, p. 

 213. The presence of the Megarhine Rhinoceros seems to be the special older feature 

 in the fauna of the Eastern Thames Brickearths. 



^ Ibid. 1 Ibid. vol. xxv., p. 217. 



" Ibid. vol. xxiii., p. 394. Geol. Mag., Vol. III., pp.. 67, 99, 348, and 398. 



