f>fihe Environs 0/ Paris, %f 



The k)wermost strata of calcareous foritiatioji are the ' 

 best characterized : they are very bandy and frequently 

 ^en, rather sandy , than calcareous. When they are soHd, 

 they are decomposed and fall into dust on the first ex- 

 posure : this kind of stone therefore is not fit to be used. 



The shelly limestone which composes it, and even tl^ 

 sand which sometimes supplies its place, almost always 

 contain green earth in** powder or in small grains. Thisr 

 earth, from our experiments, appears to be analogous to 

 terra veronica. It owes its colour to iron ; it is found iit 

 the lower strata only : we do not find it in the chalk, ia 

 the clay, nor in the middle or upper calcareous strata, and 

 we may regard its presence as a certain indication of the 

 proximity of plastic cls^y, and consequently of chalk, 

 'But what characterizes still more particularly this system 

 of strata, is the prodigious quantity of fossil shells which 

 it contains. In order to give an idea of the number of 

 species which these strata contain, it will be sufficient to 

 say that M. Defrance has found more than six hundred 

 species, all of which have been described by M- La- 

 marck. 



W'e have to rcir^ark that most of the shells of the lowest 

 of these strata are much further removed from the present 

 existing species, than those of the upper strata. We shall 

 mention among the fossils peculiar to these lower strata, 

 periwinkles, oysters, muscles, pinnae, calyptreae, pyrdce, 

 large tellines, tcrcbelloe, porpytes^ madrepores, and iparti- 

 cularly nummulites and fungites. 



Such are the names of the most remarkable shells ta 

 this stratum : we ought to remark that it was not in the 

 depot of Grignon alone that we gathered the specimens 

 we has'e described ; such examples would not have charac- 

 terized the system of straia which we wish to make out 

 readers acquainted with : we chose them from the quarries 

 of Sevres, Meudon, Issy, Vaugirard, Gentilly ; in the strata 

 of Guespelle; in those of Pallcry near Chaumont, &c. 



It is in this same stratum that we find the cameririeS'. 

 They are either by themselv-es ol'mi'xed with madrepores and 

 the preceding shells. ^ hey are always the lowe-st, and 

 consequently the first which are deposited on the chalky 

 formation ; but this is not the case every where. Wc hav® 

 found some of them near Villers-Cottefet, in the valley 

 of V^aucienne ; and at Chantilly on the flectivity of the 

 mountain. They are mixed here with shells in good pre« 

 scrvaiion, and with coarse grains of quartz, which, to-, 

 gcihcr;^ make it -a kind of .puddingstune, on Mount Ga- 

 ♦I ueloii 



