AGE OP THE LIGNITIO DETERMINED BY ITS FLORA. 355 



of a new land at and from the base of the Lignitic is sufficiently evidenced, 

 and has been recognized by every geologist who has explored the country. 

 This land, which, rising up, is cut, of course, by shallow brackish swamps or 

 estuaries, is the beginning of a whole formation of wide surface and great 

 thickness, where the plants, preserving their Tertiary characters, have con- 

 tributed the materials for the composition of the numerous coal strata, which 

 constitute an essential j^art of it. In those brackish estuaries, paleontol- 

 ogists have already recognized species of positive Tertiary relation, mixed 

 witli a few remains of Cretaceous types. But these low swamps are 

 drying up, their Cretaceous fauna is gradually reduced in its represent- 

 atives by the influence of different atmospheric circumstances, while that 

 of younger types becomes predominant. Henceforth the Cretaceous ani- 

 mals appropriate to deeper water may live still; their remains may even 

 be found hereafter mixed with recent Tertiary strata, but their presence 

 cannot modify the age of the new land formations. This admission would be 

 against reason quite as much as the assertion that we are now still living in 

 Cretaceous times, because animals of Cretaceous types are dredged from the 

 depths of the ocean. For the determination of the epochs of the land forma- 

 tion, if we may call epochs arbitrary divisions of time establislied for con- 

 venience by geologists, we have to consider the documents relating to their 

 history, and these are mostly the fossil remains of their floras. 



