246 THEORY OF THE EARTH. 



fera. It is filled with crocodiles and tortoises, but 

 the genera of extinct mammifera which the 

 gypsum contains, are not found in it : they evi- 

 dently did not exist in the country when these 

 clays and lignites were formed. 



This fresh water formation, the oldest which 

 has been distinguished in our neighbourhood, and 

 which supports all the formations which we have 

 just enumerated, is itself supported and embraced 

 on all sides by the chalk, an immense formation, 

 both as to thickness and extent, which shews it- 

 self in very distant countries, such as Pomerania 

 and Poland ; but which, in our vicinity, reigns 

 with a sort of continuity in Bern, Champagne, 

 Picardy, Upper Normandy, and a part of Eng- 

 land, and thus forms a great circle, or rather 

 a great basin, in which the deposits of which we 

 have been speaking are contained, but of which 

 they also cover the edges in the places where they 

 were less elevated. 



In fact, it is not in our basin only that these 

 various formations have been deposited. In the 

 other countries where the surface of the chalk 

 presented similar cavities for them ; in those even 

 where there was no chalk, and where the older 

 formations alone presented themselves as supports, 

 circumstances often led to the formation of depo- 

 sits more or less similar to ours, and containing 

 the same organic bodies. 



