12 M. D'Omalius D'Halloy 



on 



to the calcaire a cerites, as Messrs. Cuvier and Brongniart 

 hare already suspected. 



The calcaire a cerites formation, + which appeared to me 

 to rest immediately on the chalk between Damerie and 

 Reims, does not furnish any good building stones; its beds 

 are on the contrary loose and friable, as at Grignon, and 

 contain an immense quantity of shells. In this system of 

 hills, are found the fossils, celebrated as those of Courtagnon, 

 a name given them, because M. de Courtagnon was the first, 

 in the Chateau of the same name, to form a considerable 

 collection of these shells ; for they are equally abundant, 

 and easier to collect at Fleury, la Riviere, and Arthy, than 

 at Courtagnon. These shells are known to be generally the 

 same with those of Grignon : it could scarcely be expected 

 that two deposits so distant, should so resemble each other 



cation of sulphate of iron, and layers of shells more or less broken, 

 among which are distinguished many cerithia, and bivalves which I be- 

 lieve belong to the genus cytherea. 



The other situation is near Cluiteau-Thierry (Aisne), where the valley 

 of the Marne affords blackish clay, full of shells, among which are seen 

 many oysters, cythereee, and a cerithium resembling that of St. Margue- 

 rite. It is very probable that this deposit is situated between the chalk 

 and the calcaire a cerite, since this last forms the surrounding hillocks, 

 and that the chalk is met with about 1000 yards further up the valley. 



(Note of the Editor of the Annales des Mines.) 

 We visited this deposit in August, 1813 ; it evidently constitutes a 

 j>art of the calcaire a cerite formation, and its inferior parts are composed, 

 as the author has said, of pure plastic clay, and of plastic clay mixed 

 with sand, lignite, pyrites, and the shells mentioned by the author; 

 oysters, moreover, are there seen in great abundance. It should be ob- 

 served that this disposition is precisely the same, and with the same shells, 

 at Marly Jicar Paris, above the chalk; at Vauxbuin, near Soissons, de- 

 partment of tl',e Aisne, &c. 



+ Messrs. Cuvier and Brongniart do not mention the calcaire a cerites 

 formation, in their enumeration of the Parisian rocks (9d edition, 1829). 

 The following is the list given by them : 



