1853.] SHARPE SANDS AND GRAVELS OF FARRINGDON. 185 



M. d'Orbigny, have been much neglected in this country, and their 

 geological range is little known ; but the remaining classes furnish 

 safe grounds of comparison : of these the Farringdon gravel contains 

 33 species, found either in the Upper green sand, the Tourtia of Bel- 

 gium, or the Craie Chloritee of France. But of these 33 species only 

 the following 13 are known in the Upper green sand of England, and 

 most of these range upwards into higher strata, viz. — 



Manon peziza, also in the Maesti-icht sands. 



■ marginatum, also in the Upper chalk. 



Jerea pyriformis. 



Terebratula biplicata. 



Menardi, also in the Maestricht sands. 



Rhynchonella latissima, also in the Chalk and Maestricht sands. 



Ostraea vesicularis, also in the Upper chalk and Maestricht sands. 



Exogyra conica, also in the Maestricht sands. 



Pecten Dutemplii. 



Dianchora striata, also in the Chalk. 



radiata, also in the Chalk. 



Serpula plexus, also in the Chalk, 

 leaving only 3 species peculiar to the Upper green sand of England. 

 Out of above 70 species enumerated by Dr. Fitton from the Upper 

 green sand of the counties here referred to, only 9 are found in the 

 Farringdon gravel, and these do not include the most characteristic 

 species of that formation. 



The southern extremity of the Farringdon gravel at Fernham is 

 only two miles from the escarpment of Chalk and Upper green sand, 

 and there are no indications of any barrier having ever intervened, so 

 that, if the Farringdon beds are to be classed with the Upper green 

 sand, we must suppose the same sea to have been forming two totally 

 different deposits, and to have been inhabited by two different groups 

 of inhabitants at the distance of only two miles ; a supposition which, 

 when clearly explained, is sure to be unanimously rejected. 



We are thus driven step by step, by the exhaustion of all other al- 

 ternatives, to class the Farringdon Sponge-gravels as more modern 

 than the Chalk ; but I do not by this mean to include them in the 

 Tertiary series, with which their fauna has nothing in common, but 

 to regard them as a remaining fragment of one of the upper members 

 of the Cretaceous formation, of which the rest were destroyed by de- 

 nudation before the commencement of the Tertiary period. Other 

 relics of the upper cretaceous deposits are found in the limestone of 

 Faxoe, the calcareous sands and sandstones of Maestricht and Ciply, 

 and the pisolitic limestone of Laversine and Vigny ; and I hope on 

 some future occasion to succeed in convincing the Society that there 

 are also other deposits of the same period in England*. 



* The ferruginous sandstone which caps the hill of Seende, near Devizes, de- 

 scribed by Mr. Cunnington in the 6tli volume of onr Journal, p. 453, is undoubt- 

 edly contemporaneous with the Farringdon Sponge-gravel. I believe also that the 

 ferruginous sand and gravel of Nuneham Park and Clifton Hampden, in Oxford- 

 shire, with outlying patches at Broom Hill, Boars' Hill, and Cumner Hurst, near 

 Oxford, belong to the same period. Probably some of the ferruginous deposits 

 of Buckinghamshire and Bedfordshire, now attributed to the Lower green sand, 

 may also prove to be of the Danian formation. 



