1847.] PRESTWICH ON THE LONDON CLAY. 365 



Limited in the number of its Testacea as the whole of the ma- 

 rine tertiary series of London and Hampshire long appeared to be, 

 as compared with the French series, there now appears a prospect, 

 thanks to the zeal of Mr. Bowerbank, Mr. Wetherell, Mr. Edwards 

 and others, of finding the English fauna far richer than was antici- 

 pated. The number of described species of Testacea already known 

 in the London and Hampshire systems taken together amounts to 

 nearly 400 ; and from information given me by Mr. F. C. Edwards 

 of Hampstead, I am led to believe that, including undescribed species, 

 we may estimate them at between 600 and 700. There is little doubt, 

 I think, that they will shortly exceed even this number, especially as 

 new lines of railway intersect the London clay, our research in which 

 has been much limited by the extreme scarcity of permanent sections. 



We will confine ourselves however to the 390 described species : of 

 these 133 occur in the London clay of the neighbourhood of London, 

 193 in the strata at Bracklesham Bay, and 209 in the strata at 

 Barton Cliff's. Out of the whole number only 35 species are common 

 to all the three localities. Further, 8 are common to London and 

 Bracklesham, 1 1 to London and Barton, and 55 to Bracklesham and 

 Barton. (See list of species and table of distribution at the end.) It 

 is possible that even the small number of species now given as common 

 to these three groups of strata may yet be reduced as analogues are 

 compared. It must also be borne in mind that some species, although 

 common to all these groups, form, in each of them, distinct varieties. 

 Granting however that the localities* of the described species have 

 been correctly given, and that they have been sufficiently compared, 

 the number of London clay shells {i. e. of the London district alone) 

 occurring at Barton and Bracklesham only amounts to 5b, out of the 

 total number of 133, thus leaving 79 as peculiar to the London district. 

 When to this fact we add the occurrence of the numerous distinct 

 species of Crustacea, fishes, reptiles and plants peculiar to the London 

 district, have we not reason to doubt the contemporaneity of the 

 clays of London with the strata of Barton and Bracklesham ?— espe- 

 cially if we can show that the London clay has a much closer repre- 

 sentative in the Hampshire system in strata distinctly below the 

 Barton and Bracklesham series. 



But if the clay of London be not synchronous with those of Barton 

 and Bracklesham, in what relation does it stand to them ? 



The similarity of structure and physical conditions may indicate, as 

 we have suggested, that the thick and extensive strata of London clay 

 of the neighbourhood of London, and the lowest fossiliferous beds of 



may here take the opportunity to state the great advantages which the valuable 

 illustrated copy of this Catalogue, arranged by Mr. Morris, recently presented to 

 the Geological Society by our President, Mr. Leonard Horner, will afford to the 

 geologist. It will be a standard work of reference and authority, as the illus- 

 trations are mostly from the original works, many of which are of difficult access 

 and very expensive. 



* Some few palpable errors, where by mistake a fossil from the Barton clay has 

 been quoted as found in the clays of the neighbourhood of London, or where 

 distinct species from Hampshire and London have been considered as the same, 

 are corrected. 



2 c 2 



