GG OX THE REVOLUTION"? OF 



Of the hundred and fifty species, about a fourth are oviparous quad- 

 rupeds, and all the others are mammiferous. Amongst these, more 

 than half belong to non-ruminating hoofed animals. 



It would be premature to establish on these researches any conclu- 

 sion relative to the theory of the earth ; because they have not a ne- 

 cessary relation to the members of the genera or species which may 

 be imbedded in our layers. Thus much has been gathered from those 

 bones of the larger species, which more readily strike the workmen ; 

 whilst those of the smaller are usually neglected, unless chance brings 

 them into the hands of a naturalist, or some striking circumstance, 

 such as their abounding in certain places, should draw the attention 

 of the common observer. 



Relations of the Species with the Strata. 



What is more important, and is even the most essential object of 

 all my toil, and establishes the actual relation with the theory of the 

 earth, is to know in what layers we find a particular species, and if 

 there be any general and relative laws either as regards zoological sub- 

 divisions, or to the greater or lesser resemblance of the species with 

 those of the present day. 



The recognized laws in this respect are very remarkable arid veay 

 clear. 



First, it is certain that oviparous quadrupeds appear much more fre- 

 quently than viviparous ; that they are ever more abundant, larger, and 

 more various in the ancient layers than at the actual surface of the 

 globe. 



The ichthyosauri, the plesiosauri, many tortoises, and crocodiles, 

 are beneath the chalk in the formations commonly called those of Jura. 

 The monitors of Thuringia would be still more ancient, according to 

 the opinion of the school of Werner, if the copper slate which includes 

 them, amidst so many sorts of fishes supposed to be of fresh water 

 origin, be amongst the most ancient beds of secondary formation. 

 The immense crocodiles and great tortoises of Maestricht are even in 

 the chalky layer ; but these are marine animals. This first appear- 

 ance of the fossil bones seems then to prove that there were dry lands 

 and fresh waters before the formation of the chalk; but neither at 

 that epoch, nor whilst the chalk was forming, nor even long after- 

 wards, was it incrusted with the relics of terrestrial mammifera ; at 

 least the small number of those alleged to have been found form only 

 an exception perfectly immaterial. 



We begin to find the bones of marine mammifera, that is, of laman- 

 tins and seals, in the thick shelly limestone which is above the chalk 



