112 



Ostrece of the uppermost chalk. The beds 8 and 9, Craie chloritee 

 and Gres vert, containing, axm^Exogyroi and some cretaceous fossils, 

 the Pecten qiiinque-costatus and P. orbicularis, most unequivocally 

 rejjresent our Upper Greensand or "malm rock." The marly strata 

 which lie beneath such beds are therefore, we may fairly presume, 

 the representatives of the English gault ; and, lastly, the yellow lime- 

 stone and sand, immediately beneath it, which forms the Neocomian 

 of M. Dubois, may, after all, be considered the equivalent of our 

 Lower Greensand, or the expansion of its lowest beds which pass 

 into the Wealden. 



I have always regretted that so few foreign geologists have ob- 

 tained an adequate idea of the dimensions an,d importance of the 

 third or inferior division of lower greensand as exhibited on the 

 southern shores of the Isle of Wight (Atherfield Rocks). In France 

 the formation has been little recognized beyond the BouUonnais, 

 where it has already almost lost its distinctive characters, and where 

 thei'e are no longer the divisions of upper, middle and lower beds, • 

 each, as shown by Di*. Fitton, characterized by peculiar fossils. In 

 the south and east of France, where upper greensand and gault 

 abound, it now appears* that the base of the Cretaceous system is 

 composed of limestones identical with those of Neufchatel, and which, 

 participating in all the flexures of the chalk, are usually broken off, as 

 in the Crimea, from the Jurassic system. 



It has been suggested that the Neocomian limestones may re- 

 present the Wealden of British geologists. But this is not, so far 

 as I can judge, safe reasoning; for the latest researches of Professor 

 Owen would lead me to believe, that the Saurians of that great 

 estuary formation are much more nearly allied to those of the Oolitic 

 or Jurassic epoch than to those of the Cretaceous period-]-; and 

 Agassiz has assured us that the fishes of the Wealden are entirely 

 distinct from those of the chalk. 



I have before expressed my opinion on the head of Neocomian, 

 both to French and English geologists J, and I now repeat it, more 

 however as a stimulus to those who have the means to settle this 

 point accurately, and not because I entertain any objection to the 

 foreign use of the M'ord. The term may, indeed, be very well and 

 appositely used in reference to the deposit throughout central and 

 eastern Europe, where its lithological characters are so different 

 from what is I presume the English type ; and where they have 

 been so well described by Swiss and French observers. I seek 

 merely for the establishment of the truth ; and I again ask if the 

 Neocomian of Neufchatel and the Crimea be not the equivalent of 

 the lowest Greensand of England, and of the Mls-thon of Rdmer in 

 Hanover? On revisiting the Isle of Wight last spring, in company 



* Soe discourse of last year. 



f See note p. 89, on the supposed Wealden of the Highlands. 



X In refevring to an opinion which I expressed at the meeting of the 

 Geological Society of France in 18o9 (Bull. Soc. Geol. torn. x. p. 392 et 

 seq.), I beg to say, that it is specially to the Greensand as the chief equiva- 

 lent to which I refer. 



