282 



MINERALOGY OF THE ENVIRONS OP PARIS. 



formations sometimes terminate with a bed of clayey 

 iand, in which no petrifactions occur. 



The whole of the beds, from the layer immediately 

 over the marine limestone, to that containing the oysters, 

 constitute the gypsum formation. Guvier considers them 

 as constituting two formations, viz. the gypsum and ma- 

 rine marl formations. It is, however, evident that all the 

 beds belong to one formation, because they exhibit all 

 those relations which occur in sets of strata, considered 

 as belonging to the same formation. 



In the following Table are enumerated the petrifac- 

 tions that belong to the gypsum, and to the marine for- 

 mation which rests on it. 



