THEORY OF THE EARTH. 97 



trace of this class in any of the deposits preceding 

 those which rest upon the coarse limestone. Cer- 

 tain lignites and molasses do in fact contain 

 them ; but I am very doubtful whether these de- 

 posits are all, as is commonly supposed, anterior 

 to that limestone. The places where these bones 

 have been found are so limited, both in extent 

 and in number, as to induce us to suppose some 

 irregularity, or some repetition of the formation 

 containing them. On the contrary, the moment 

 we arrive at the deposits which rest upon the 

 coarse limestone, the bones of land-animals pre- 

 sent themselves in great abundance. 



As it is reasonable to believe that shells and 

 fishes did not exist at the period of the forma- 

 tion of primitive rocks, we are also led to con- 

 clude that the oviparous quadrupeds began to ex- 

 ist along with the fishes, and at the commence- 

 ment of the period during which the secondary 

 rocks were formed ; but that the land-quadrupeds 

 did not appear upon the earth, at least in any 

 considerable number, till long after, and until 

 the coarse limestone strata, which contain the 

 greater number of our genera of shells, although 

 of species different from ours, had been depo- 

 sited. 



It is remarkable that those coarse limestone 

 strata which are used at Paris for building, are 

 the last formed strata which indicate a long and 



a 



