1869.] DAWKINS BRITISH POSTGLACIAL MAMMALS. 217 



Mr. W. Boyd Dawkins, in reply, admitted that possibly some 

 animals classed as Postglacial belonged also to the Glacial period ; 

 but for convenience' sake he had adopted the three divisions in the 

 paper. He saw no necessity for any of the animals being of purely 

 southern origin. He did not identify the Lower Brick-earth of the 

 Thames valley with the other river-deposits, though, from the 

 presence of the Musk-sheep, he was inclined to place them later than 

 at one time he did. The only reason he could give for the absence of 

 Preglacial caves both in England and on the Continent was, that the 

 rocks containing them may have been removed by denudation. 



