186 I'KOCKKDINGS Ol' THE GEOLOGICAL SOCIETY. [NoV. 30, 



The long interval which intervened between the tbrniation of the 

 uppermost chalk, and the first tertiary bed was a period of denuda- 

 tion, in which the chalk was entirely removed from some places, and 

 its u])per portion washed away from others ; the deposits formed 

 during this period were likely to contain coarse and water worn ma- 

 terials, like that under consideration ; and it is surprising that we 

 find so few traces of such deposits. 



The organic remains of the Chalk are in a great degree peculiar to 

 that formation ; but there are many species 'common to the Upper 

 green sand, the Tourtia, the Maestricht sand, and the Farringdon 

 gravels which are not found in the Chalk itself* : all of those de- 

 posits were formed in comparatively shallow water not far from a 

 coast, and their fossil species naturally differ from those of the Chalk 

 which lived in a deep open sea. The following hypothesis will ex- 

 plain our finding the same species above and below the Chalk, but not 

 in the Chalk itself : during the formation of the Chalk the laud was 

 gradually sinking, and the ocean consequently extending itself; as 

 long as this process continued the deep-sea deposit of the Chalk would 

 be gradually spread over the littoral deposit of Upper green sand 

 previously accumulated round its shore ; but when at a later period 

 a rise of the land took place, reducing the ocean to narrower limits, 

 littoral deposits would be accumulated above the Chalk, as has taken 

 place at Maestricht. In this view the Upper green sand and the 

 Maestricht sands appear to be continuous deposits formed round the 

 edge of the same ocean, at periods when its limits were dilierent ; 

 and an explanation is afforded of the large number of species common 

 to those two formations which are usually regarded as entirely 

 distinct, because they are separated by the whole thickness of the 

 Chalk. 



The organic remains of the Sponge-gravels of Farrmgdon have 

 much less in common with the fauna of the Blackdown sands than 

 with that of the Upper green sand proper ; for no species character- 

 istic of Blackdown has been found at Little Coxwell ; and the only 

 species common to the two localities are such as had a long range 

 through the cretaceous series. The Blackdown sand, as is well 

 known, contains many Gault species not found elsewhere in the Upper 

 green sand. Mr. Austen suggested (1. c. p. 4/2) that the Gault was 

 a deep-sea deposit synchronous as a whole with the Upper green sand. 

 The observations here recorded lead me to modify that view, and to 

 suggest that the Blackdown sand was the littoral deposit of the 



* The proof of this will l)e found, not only in the list appended to this paper, 

 but by reference to Goldfuss, whose work contains descriptions of 14 species 

 common to i\Iaestricht and the Upper green sand, only 3 of which occur in the 

 Chalk. In a note upon Manon peziza, vol. i. p. 243, Goldfuss remarks, " Es ist 

 iibrigeus nierkwiirdig, dass raehrere Petrefacteu des St. Pctersberges audi hier 

 (Essen an der Ruhr) jedoch gewiJhnlich mit einem etwas abweichcuden Habitus, 

 vorkommen." The Calcaire pholitique of Laversine, near Beauvais, is in the same 

 case; M. d'Archiac says of it, " 11 est remarquable qu'on y ait trouve si peu 

 d'especes de la craie blanche, avec laquelle ce lambeau est en contact, tandis qu'il 

 y a un assez grand nombre qui sent identiques avec celles de pays fort eloigm-es 

 et avec celles de la craie tufeau." 



