THEORY 0F THE EARTH. 113 



vers the chalk strata in the neighbourhood of 

 Paris. But no bones of mammiferous land-quad- 

 rupeds are to be found in that formation ; and 

 notwithstanding the most careful investigations, 

 I have never been able to , discover the slightest 

 traces of this class, except in the formations which 

 lie over the coarse limestone strata ; but imme- 

 diately on reaching these more recent formations, 

 the bones of land-quadrupeds are discovered in 

 great abundance. 



As it is reasonable to believe that shells and 

 fish did not exist at the period of the formation of 

 the primitive rocks, we are also led to conclude 

 that the, oviparous quadrupeds began to exist 

 along with the fishes, and at the commencement 

 of the period which produced the secondary for- 

 mations; while the land-quadrupeds did not ap- 

 pear upon the earth till long afterwards, and un- 

 til the coarse shell limestone had been already 

 deposited, which contains the greater part of our 

 genera of shells, although of quite different species 

 from those that are now found in a natural state. 



It is remarkable that those coarse limestone 

 strata, which are chiefly employed at Paris for 

 building, are the last formed strata which indicate 

 a long and quiet continuance of the water of the 

 sea above the surface of our continent. Above 

 them, indeed, there are found formations contain- 

 ing abundance of shells and other productions of 



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