the Environs of Paris. .il3 



In this particular,* for, with few exceptions, the same species 

 are distributed in a similar manner. But with respect to 

 preservation, the shells at Courtagnon excel those of Grignon ; 

 they are harder, less white, and possess a pearly appearance, 

 resembling recent shells. The calcaire grossier containing 

 them has a yellow tint, approaching more the colour of ochre 

 than at Grignon ; in some places it is quite friable, in others 



SECONDARY ROCKS. 



Sub-formations and principal 

 Formations. Rocks composing them. 



I. Ancient marine formation 1. Chalk. 



TERTIARY ROCKS. 



f Plastic Clay. 



II. First freshwater formation 2. < Lignite. 



d First Sandstone. 



f Calcaire grossier, and the 



III. First marine foi-mation 3. •< Sandstone that it some- 



^.times contains. 

 r4. Siliceous limestone. 



IV. Second freshwater formations • • • • -s 5_ 5 Gypsum with bones. 



C ' I Freshwater marls. 

 (~6. Marine gypsum marl*. 

 I (Thirduppermarinesand- 



V. Second marine formation] "a 7. -^ stone and sand. 



I '^ Upper marine limestone 

 L (^ and marls. 



f Millstone without shells. 

 VI. Third and last freshwater formation .. < Millstone with shells. 



CUpper freshwater marls. 



The calcaire a cerites appears to be included in the calcaire grossier; 

 as the author always speaks of it under the former name, I have not 

 thought myself at liberty to alter it. — (Translator.) 



• It may be said that the deposit of shells observed at Grignon, owes 

 its celebrity to the number, the beautiful preservation of the shells that it 

 contains, and the facility of procuring them entire ; but the bed of which 

 this deposit forms a part is not wanting in any place where even patches 

 of calcaire a cerites occur, and it perhaps extends to greater distances 

 than is supposed. This is not the place to give proofs of this opinion; 

 the Grignon bed is found not only in the Paris basin, but also on its out- 

 skirts, every time the calcaire a cerites is sunk through ; this bed, it is true, 

 will not forcibly strike observers, except when, being friable, the shells 

 may be obtained entire, as at Perne ; at Vivray, near Liancourt; at Mont 

 Ouen, and Mont Javoult, near Gisors ; at Septeuil, to the SW. of Mantes, 

 &c. — (Note of the Editor of the Annales des Mines). 



