102 THEORY OF THE EAUTH. 



ceived appropriate specific characters; and such 

 geologists as are disinclined to adopt the different 

 epochs which I have endeavoured to establish with 

 regard to fossil hones, may, for many years to come, 

 draw from thence an argument against my system, 

 so much the more convenient as it is contained in 

 my own work. 



But allowing that these epochs are liahle to 

 some objections, from such as may only consi- 

 der some particular case, I am not the less satis- 

 fied, that those who shall take a comprehensive 

 view of the phenomena, will not be checked by 

 such inconsiderable and partial difficulties, and 

 will be led to conclude, as I have done, that there 

 has been at least one, and very probably two, suc- 

 cessions in the class of quadrupeds, previous to 

 that which at the present day peoples the surface 

 of the earth. 



Proofs that the Extinct Species of Quadrupeds are not 

 varieties of the presently existing Species. 



I now proceed to the consideration of another 

 objection, one, in fact, which has already been 

 urged against me. 



Why may not the presently existing races of 

 land quadrupeds, it has been asked, be modifica- 

 tions of those ancient races which we find in a 

 fossil state ; which modifications may have been 

 produced by local circumstances and change of 



