212 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [Feb. 24, 



§ 12. The Age of the Lower Brick-earths of the Thames Valley, and 

 of the deposit at Glacton. — In the foregoing Table of distribution of 

 British Postglacial Mammals I have not classified the river- deposits 

 of Clacton, Grays, llford, and Crayford with those undoubtedly Post- 

 glacial, because of the conflicting evidence of their faunas as to their 

 true place in the geological scale. The list of Mammalia found in 

 them is inserted in the Table of distribution immediately after those 

 from the forest-bed. We will proceed to sum up the whole of the 

 palseontological evidence which they offer. 



The occurrence at Clacton * of the Rhinoceros leptorhinus of Owen, 

 of Elephas antiquus, Hippopotamus major, Irish Elk, Horse, and 

 Urus may be accounted for equally well by the assumption of its 

 Pre- or Postglacial age; for these animals dwelt in Europe both 

 before and after the Glacial epoch. A new species of Deer, Cervus 

 Browni, is closely allied to the Pallow Deer that ranges in a wild 

 state only over the warm districts around the Mediterranean. The 

 Bison points in the Postglacial direction ; but it will most probably 

 be proved by future investigations on the Continent to have lived 

 in Europe during the Preglacial period. At least the number of 

 Pregiacial localities that have been examined is not sufficiently large 

 to give value to the induction that, because it has not been noted, 

 therefore it did not exist. For the most part it has been con- 

 founded by naturalists with the Urus and Bos longifrons. The 

 Cave-lion, on the other hand, has been so well determined that the 

 balance of evidence is in favour of its Postglacial age. With its 

 exception, then, there is nothing that forbids the supposition of the 

 Preglacial age of the deposit ; but nevertheless, since the charac- 

 teristic mammals of the Forest-bed 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 Postglacial mammals are also absent, it cannot be said 

 to belong to the class of deposits that contain 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 

 Preglacial and 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 forms. 



The Lower Brickearths of the Thames Valley at llford. Grays 

 Thurrock, and Crayford contain the remains of Rhinoceros mega- 

 rhinus, which has not yet been yielded, in France, Germany, or 

 Italy, by any strata of later age than the Pliocene, and are therefore 

 brought into more intimate relation with that epoch than any other 

 of the deposits undoubtedly Postglacial. But nevertheless the 

 evidence afforded by the Mammoth, Tichorhine Rhinoceros, Cave- 

 lion and Cave-hyaena is in favour of their Postglacial date. And this 

 inference is strongly corroborated by my discovery of a skull of a 

 Musk- sheep at Crayford since the essay on the Lower Brickearths 

 was written f. How, then, can we reconcile the clash of evidence ? 



* Geol. Magazine, vol. v. p. 213. 



t Quart. Journ. Geol. Soc. May 1867, p. 91. 



