448 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [June 7, 



of the Maestricht period, was followed by subsequent depressions 

 which led to the transgressive accumulation of the Lower Tertiaries 

 from north to south. This elevation, I believe, laid dry the Chalk 

 in some direction southward, and would therefore induce one to look 

 to the north for a more uninterrupted succession of the Upper Creta- 

 ceous and Lower Tertiary strata. I am now speaking with reference 

 only to that part of the north of Europe over which the Paris, Belgian, 

 and English Tertiaries extend. I have before shown the probabihty 

 of the existence of dry land to the south and an open sea to the north, 

 during the Thanet Sands period, and of more insular conditions during 

 the Woolwich and Reading series period ; and now with respect to the 

 London Clay, the evidence tends in the same direction. With one 

 exception, which proved unimportant, I have never found any 

 transported rock-fragment in the London Clay that would enable me 

 to infer the direction of the land and its main rivers during that 

 period. If, however, we take the evidence afforded by the organic 

 remains, we shall obtain some peculiar results. If, for example, we 

 look to the Molhxscs and the Plants, we at once perceive a want of 

 accordance between them ; we find in the former an absence of that 

 group of markedly tropical forms which seem to have flourished in 

 the later sea of the Bracklesham period. The prevailing genera 

 are, on the contrary, mostly such as could live in colder regions. 

 Taken altogether, it rather indicates a moderate than a tropical 

 climate, and yet the flora is, as far as we can judge, certainly 

 tropical in its affinities. It is interesting to observe at this early 

 Tertiary period the same evidence of those climatal conditions 

 dependent upon latitude which become more strongly marked as we 

 approach our own period ; for these differences in the fauna and 

 flora arise, I believe, from the circumstance that the London Clay was 

 deposited in a sea open to the north, and therefore with an in-set of 

 cold currents determining the existence of a group of molluscs, such 

 as we might expect to find inhabiting waters of moderate tempera- 

 ture ; whilst, judging from the quantity mid extent of detritus, there 

 probably existed to the south an extensive continental area, through 

 which flowed a large river which brought down the sediment 

 forming the London clay, and all the marvellous remains of plants 

 and of land and freshwater remains entombed in it — remains wliich 

 seem to point to a vegetation of hot or even tropical climates, and to 

 a land fauna in keeping with such a temperature. If this were the 

 case, then we should have during the London-Clay period a conti- 

 nental area stretching southward of England and the north of 

 France, and a sea spreading to the northward of this laud ; while 

 the subsequent accumulation of the Bracklesham Sands took place 

 after the submergence of that land and the immigration of a marine 

 fauna from more southern seas, into which some few only of the 

 forms of the older sea were continued, — geographical conditions which 

 I hope, in a subsequent paper, to show to be in perfect accordance 

 with the limited range southward of the London Clay and the 

 correlation of the Bracklesham Sands with the wide-spread deposits 

 of the Calcaire grassier and other associated beds of the Paris Ter- 

 tiaries. 



