272 MINERALOGY OF THE ENVIRONS OF PARIS. 



Brongniart, appear to be arranged in the following order, 

 from below upwards. 



1. The chalk formation, with flint. 



2. Plastic clay, with sand (argile plastique.) 



3. Coarse marine limestone (calcaire grassier), with its 

 marine sandstone (gres marine inferieur.) 



4. Siliceous limestone (calcaire silicieux). 



5. Gypsum and marl, containing bones of animals 

 (marnes du gypse d'ossements.) 



6. Marine marl, abounding in bivalve shells ; and the 

 upper layers, abounding in oyster shells. 



7. Sandstone and sand, without shells. 



8. Upper marine sandstone (gres marine superieur.) 



9. Millstone, or buhrstone, without shells (meuliere sans 

 coquilles.) 



10. Flint and siliceous limestone or the upper or se- 

 cond fresh water formation, millstone, flint, and limestone 

 (terrein d'eau douce superieur , meuliere, silex, et calcaire.) 



11. Older and newer alluvial deposites (Limon d'atter- 

 rissement.) 



FIRST FORMATION. 



Marine Origin. 



Chalk. 



This chalk agrees, in external characters, with that 

 found in other countries. It occurs in indistinct hori- 

 zontal strata, in which we observe either interrupted lay- 

 ers or tuberose shaped masses of flint, which pass into the 

 chalk at their line of junction, or kidneys of hard chalk, 

 having the same shape and position with the flint. This 

 formation is well characterized by the petrifactions it con- 

 tains, which differ not only in the species, but sometime? 



