﻿158 PLEISTOCENE MAMMALIA. 



§ 3. Range in Time in Britain. — We have now to discuss the palseontological value 

 of the remains of the animal in determining the age of the deposits in which they are 

 found. On a reference to the foregoing Table it will be seen that the animal occurs more 

 or less abundantly in Bone-caves and River-deposits that are beyond all doubt of Post- 

 glacial age, that is to say, which contain the remains of the arctic group of animals that 

 invaded Western Europe during the great refrigeration of temperature at the close of the 

 Pliocene epoch, such as the Mammoth, Musk-sheep, and Reindeer, and that spread over 

 the area that had been occupied by the Glacial sea as the land gradually rose again above 

 the waves. There are, however, in Britain certain deposits which contain the remains of 

 Post-glacial mammals associated with those which have been considered characteristic of 

 the Pliocenes of France, Germany, and Italy, and which, therefore, stand intermediate in the 

 geological scale between Pre- and Post-glacial deposits properly so called. In two of these 

 the Cave Lion has been found, in the ancient river-bed at Clacton, and in the Lower Brick- 

 earths of the Thames Valley, at Ilford in Essex, and Crayford in Kent. We will, therefore, 

 sum up the whole of the palseontological evidence as to their place in the geological scale. 



The occurrence at Clacton of Rhinoceros ieptorhinus of Owen (R. hemitcechus of Fal- 

 coner), of fflephas antiques, Hippopotamus major, Irish Elk, Horse, and of Urus, 

 may be accounted for equally well by the assumption of its Pre- or Post-glacial age, for 

 these Pliocene animals dwelt side by side in the same area with the arctic group of 

 mammalia during the Post-glacial epoch. A new species of Deer, Cervus Brownii, 

 is closely allied to the Fallow Deer, that is now found wild only in the districts adjacent 

 to the shores of the Mediterranean. The Bison is the only animal that points in 

 the Post-glacial direction, and this even will very probably be proved by future 

 investigations on the Continent to have lived in France, Germany, and Italy during 

 the Pliocene period. With its exception, therefore, there is nothing to forbid the 

 supposition of the Pliocene age of the deposit; but, nevertheless, as the characteristic 

 mammals of the Pliocene, so abundant in the Forest-bed of Norfolk and Suffolk, are 

 absent, it would be hazardous to ascribe it to that age. And in the same way, since the 

 Reindeer, Mammoth, tichorhine Rhinoceros, and other equally common and characteristic 

 Post-glacial mammals, are also absent, it cannot be said to belong to the class of deposits 

 containing their remains. We are, therefore, justified in assuming that it represents, in 

 point of geological time, an epoch during which some of the more hardy Pliocene species 

 lived under a temperature too severe for the more delicate of their congeners, and not 

 cold enough for the invasion of the Reindeer and the allied arctic mammals. 



The Lower Brickearths of the Thames Valley at Ilford and Crayford contain the 



remains of Rhinoceros megarhinus, which has not yet been found in France, Germany, or 



Italy in any strata later than the Pliocene age, and are therefore brought into more 



intimate relation with that epoch than any other of the deposits undoubtedly Post-glacial. 



Nevertheless, strange to say, since the Essay on the " Lower Brickearths " x was written, 



1 ' Quart. Geol. Journ.,' May, 1867, " On the Age of the Lower Brickearths of the Thames Valley," 

 by "W. Boyd Dawkins, M.A., F.G.S. 



