as items of Geological Time. 



343 



The connexion of this question with the principal subject of thia 

 paper, that of the comparative value of different geological eras as items of 

 geological time, is obvious. I feel that this subject is one of great 

 difficulty ; and, as far as I know, this is the first time that any attempt 

 of the kind has been made to solve the problem. If my method be incor- 

 rect, it may yet help to suggest a better way to some one else ; and in the 

 meanwhile, even if partly heterodox, I hope it may deserve toleration. 



Classification of Faunas (Terrestrial, Freshwater, and Estuarine) 

 into Groups. 



The letter E. means English, C. Continental and not known in England ; but as the 

 physical phenomena connected with the Continental strata in which they are found are in 

 the mam, identical with those that affect the English rocks, the European Continental 

 genera are named in this Table. 



