MARINE LIMESTONE FORMATION. 



Cerithum giganteum. 

 Lucina lamellosa. 

 Cardiura porulosum. 

 Voluta cithara. 

 Crassatella lamellosa. 

 Turritella multisulcata. 

 Ostrea flabellula. 

 Cymbula. 



Second System of Strata. 



The limestone of these strata is of a grayish yellow co- 

 lour, is in part oolitic, or composed of small roundish 

 grains, and contains remarkable cotemporaneous cavi- 

 ties, that traverse the strata, and which are filled with 

 loam, sand, and flint. It is still very rich in shells ; 

 nearly all the bivalves found by M. Defrance at Grignon 

 belong to it. It also contains a few impressions of 

 leaves and stems of vegetables, and single fresh-water 

 shells. The most characteristic petrifactions of this sysr 

 tern of strata are the following. 



Cardita avicularia. 



Orbitolites plana. 



Turritella imbricata. 



Terebellum convolutum. 



Calyptrasa trochiformis. 



Pectunculus pulvinatus. 



Citheraea nitidula. 

 elegans. 



Miliolites It is very abundant. 



Cerithium Probably several species ; but neither the 

 lapidum and petricolum, nor cinctum and 

 plicatum, which latter belong to the second 

 marine formation which covers the gypsum. 



