1869.] COQUAJ^D CEETACE0U8 STRATA. 243 



interesting fauna, which comprises a large number of species, all pe- 

 culiar to the limited country of which we are speaking. It is neces- 

 sary, therefore, to admit that there is a Wealden in the Upper as 

 well as in the Lower Chalk. 



The repeated alternations which have taken place between truly 

 marine and fluvio- carbonaceous deposits, is a fact well worthy of 

 notice in the history of the Cretaceous formation of the Mediter- 

 ranean coast. Thus we have ascertained* that the great accumu- 

 lations of combustible matter of the Province of Ternel, in the 

 Kingdom of Arragon, belong to the Aptian stage. In the De- 

 partment of the Gard, and at Mondragon, the coal worked belongs 

 to the Middle Chalk. At Sainte Baumef the Provencian lime- 

 stones contain jet with amber, which has been the object of some 

 research. Lastly, the great industrial works which supply the 

 market of Marseilles with coal are opened in the Santonian and 

 Campanian stages, stages which, in the counties of Kent and Sussex, 

 as well as in the environs of Paris, are remarkable for the purity and 

 whiteness of the chalk of which they are composed. 



It would be not merely dangerous, but impossible, to establish a 

 comparison upon the petrographic character of countries distant 

 from each other, since our chalk in the south only furnishes hard 

 limestones employed in large building-woTks, sandstones with which 

 the streets of Marseilles are paved, black limestone, black clay and 

 coal. But, in spite of this difference in the composition of the rocks, 

 there exists a principle which furnishes a sure means of establishing 

 comparisons, in which mineralogy cannot assist. This principle lies 

 in the examination of the faunas. Thus, although England is de- 

 prived of the legion of Eudistes which have rendered the chalk of 

 our country so celebrated, she nevertheless possesses a considerable 

 quantity of fossils identical with ours, by means of which it becomes 

 easy to establish strict synchronisms for the corresponding stages, 

 just as it is easy to show that the chalk of Provence is much more 

 complete than that of Great Britain and the basin of the Seine. 

 Whence I conclude that, if a general classification of the Cretaceous 

 formation were now to be attempted by an international Geological 

 Congress, the preference ought to be given to Provence, on account 

 of the facility of finding there larger and more numerous divisions — 

 in one word, more classical types. 



To any one acquainted with the mountains of Provence, the ge- 

 ology of Algeria offers no very serious difficulty. The Cretaceous 

 formation of the elevated plateaux of the Atlas seems to have been 

 copied from Provencal models (fig. 4). Above the Lower Greensand 

 and the Speeton Clay, we find the same succession of stages as in 

 the south of Prance ; but they are generally richer in fossil species, 

 especially in Ostrece and Echinoderms. 



* Monographie Paleontologique de I'etage Aptien de I'Espagne, 1862. 



t Description Geologique du Massif Montagneux de la Sainte Baume, 1866. 



