4S On the Mineralogical Geograpui/ 



fielon near Compicgne, and Mount Ouiii near Gi-* 

 8drs, &c. 



Another character peculiar to the shells of this stratura 

 is, that they are mostly very entire and well preserved, be- 

 ing easily detached trom their rock_, and some of them 

 have preserved their pearly state. In all th^j preceding 

 places, and in others, this is less remarkable ; because we 

 ascertained that the sandy calcareous strata, which containt 

 these shells, immediately follow the plastic clay which covers 

 the chalk ; and it is by these multiplied observations that 

 we recognized the generality of the scale which we have 

 laid down. 



The other systems of strata are less distinct, and we 

 have not as yet been able to arrange the numerous obser- 

 vations which we have made, in order to establish witli 

 precision the succession of the different fossils which ought 

 to characterize them. We can announce, however, that, 

 from our inspection of the quarries to the south and west 

 of Paris, from Gentilly to Villepreux and Saint-Germain, 

 the strata above those which we have described succeed 

 each other in the following order. 



1. A soft stratum frequently of a gree^iish colour, this is 

 called the green bank by the workmen. It frequently ex- 

 liibits on its lower surface brownish marks of leaves and 

 stalks of vegetables. 



2. Gray or yellowish strata, sometimes soft, sometimei 

 very hard, and containing chiefly roundish venuses, cam- 

 preys, and particularly luberculated cerites> which last arc 

 sometimes in prodigious quantity. The upper and middle 

 part of this stratum, frequently hard, is a very good stone 

 building, and is known by the name of the rocfi. 



3. Lastly, and towards the upper part, a stratum, not 

 thick but hard, which is remarkable from the prodigious 

 quantity of small long and striated tellines which it pre- 

 sents in its seams. These tellines are laid horizontally, 

 and closely wedged against each other. They are generally 

 white. 



Above these last strata of coarse limestone we find hard 

 calcareous marlcs divided into fragments, the faces of which 

 are generally covered with a yellow coating and with black 

 dendrites. These niarles are separated by soft calcareous- 

 marles, by argillaceous marlcs, and by calcareous sjind, which 

 is sometimes agglutinated, and it contains horny silex with 

 horizontal zones. We refer to this system the stratum of 

 the quarries of Neuilly, in which we find crystals of quart* 

 and rhomboidal crystals of variegated carbonate of lime. 



