Yol. 50.] FAUNA FROM THE IGHTHAM FISSURE. 207 



■with thern, but which have not before been recorded from beds of 

 so early a date. I am disposed, therefore, to regard all the species 

 found in this fissure, except the rabbit, as of Pleistocene age. 



One of the most interesting species found in the Ightham fissure 

 is the reindeer, which has also been met with at Boughton, 

 Otterham, and Sittingbourne. It is a remarkable fact that 

 although this species is abundant in the Thames Valley west of 

 London, and has also been found both to the north and south of 

 the lower parts of the Thames Valley, as well as in many Caves, 

 it has never been met with in the brick- earth of the Thames Valley 

 itself to the east of London. This circumstance, combined with 

 the occurrence of Rhinoceros megarhinus in these deposits of the 

 Lower Thames Valley, led Prof. Boyd Dawkins to regard the latter 

 deposits as of an earlier date than those containing remains of 

 reindeer, but without the megarhine rhinoceros ; and while advo- 

 cating for them a very early Pleistocene origin, 1 he acknowledged 

 that they were certainly of later date than the Norfolk Porest Bed. 



About thirty species of mammals have been found in the brick- 

 earth of the Lower Thames Valley, and half of these occur in the 

 Ightham fissure, but if Prof. Boyd Dawkins's separation of the 

 former deposits as representing an earlier part of the Pleistocene 

 be correct, then the presence of the reindeer at Ightham would 

 prevent that deposit from being regarded as of the same age as the 

 Lower Thames Valley brick-earth, and point to a relationship with 

 some other part of that period. Indeed, there can be little doubt 

 that, whatever may prove to be the relation of the Lower Thames 

 Valley brick-earth toother Pleistocene deposits, the Ightham-fissure 

 fauna is most nearly related to that which is found in British 

 Cave-. 



Much interest attaches to a correct knowledge of the climate 

 prevalent during the Pleistocene period, indications of which are to 

 be found in the Arctic Freshwater Bed of Norfolk, the Boulder 

 Clay, and the animals which are found in the various deposits. 

 The probability of alternations of warmer and colder periods during 

 Pleistocene times has long been advocated ; but it has been thought 

 possible by some that, with a more continental climate than at 

 present prevails in Britain, the alternations of summer and winter 

 might be sufficient to account for the seeming mixture of species. 

 The latter supposition, however, seems scarcely tenable. 



Recently the possibility of steppe conditions having extended 

 much farther westward in Pleistocene times has been advocated 

 by Dr. Woldrich,- by Dr. Nehring, 3 and my colleague Mr. Clement 



1 Quart. Journ. Geol. Soc. vol. xxv. (1869) p. 212. 



2 ' Die diluvialen Faunen Mitteleuropa9,' Mitth. Anthrop. Gesellsch. Wien, 

 vol. ii. 1882. 



3 ' Ueber Tundren unci Steppen der Jetzt- und Vorzeit,' Naturwissensch. 

 Wochenschrif't, vol. v. (1890) pp. 451 and 47") ; see also separate work, published 

 at Berlin, 1890. 



