liv PROCEEDINGS OF THE GEOLOGICAL SOCIETY. 



London Clay. Bracklesham. Common. 



Fish 83 28 10 



Mollusca 224 372 56 



Articulata 27 13 4 



Echinodermata .... 17 1 



Zoophyta 10 16 



Foraminifera 23 9 



Plantse 106 3 2 



Total 515 450 72 



In a second portion of this paper the author draws attention to a 

 very remarkable and significant circumstance ; viz. the amount of 

 agreement between the lower Loudon Tertiaries and the upper beds 

 of the underlying Chalk. He particularly instances the Thanet 

 Sands and the lower Landenian system of Dumont in Belgium, the 

 faunae of which have a general fades so closely resembling that of 

 analogous groups in some of the cretaceous strata, that they, and 

 particularly the Belgian beds, have by some been considered as cre- 

 taceous rather than tertiary. Other cretaceous fossils are shown to 

 range upwards into still younger formations of the London basin. 



I shall not pretend to go through the arguments brought forward 

 by Mr. Prestwich ; the paper is one which deserves the particular 

 attention of every palaeontologist. I will only make one observation on 

 the concluding statement, *' that the London clay presents in many 

 of its generic forms a closer approach to those now existing in our 

 climate than the Bracklesham sands." This remark appears to me 

 to offer additional difficulties to our endeavours to define with any- 

 thing like accuracy, on palseontological grounds alone, the respective 

 limits of the different tertiary epochs. If we find, in consequence of 

 the physical and geographical features of the seas in which these 

 tertiary organisms were deposited, that the fossils of the older forma- 

 tions resemble living forms more closely than those deposited during 

 the intervening period, how can we attempt, on fossil evidence alone, 

 where superposition does not come to our assistance, to determine the 

 relative ages of formations situated at a distance from and indepen- 

 dently of each other 1 Physical changes influencing the conditions of 

 life must have occasioned numerous oscillations of the earth's surface ; 

 and if this observation is confirmed, we must conclude that they have 

 so modified the character of the ancient seas as to have brought back 

 forms of an older date, hitherto supposed to have died out. We have 

 thus impoeed upon us a task of more than ordinary difficulty, and 

 one requiring no ordinary caution before we can hope satisfactorily 

 to unravel the order of creation, or to define the relative periods in 

 which many of the European tertiary formations were deposited. 



In a subsequent paper, of which as yet a short abstract only has 

 been published, Mr. Prestwich has communicated to us his views on 

 the correlation of the lower tertiaries of England with those of France 

 and Belgium. The author is known to have had so many oppor- 

 tunities of examining these different formations, that his opinions are 

 entitled to the greatest consideration ; they are put forward with a 



