338 A SYMPOSIUM 



(<5) But I much doubt that these are coordinate with 

 Devonian. 



8. " Mississippian " serves our American purposes well, but, 

 if used, ought to be coupled with Lower Carboniferous as syno- 

 nym, as you have done. 



9. Cretaceous ought to be divided into two coordinate 

 divisions, but I do not think these are at all coordinate with 

 Triassic, Jurassic, or Devonian. They must be regarded as 

 sub-periods. 



10. I think it best, therefore, to retain the names Lower and 

 Upper Cretaceous ; but, if a new name is used for the lower 

 division, why not call it " Shasta." It was certainly first recog- 

 nized there. 



11. I am in favor of the fourfold division of Cenozoic you 

 propose, although I fully appreciate the reasons for uniting 

 Miocene and Pliocene into Neocene. Tertiary and Quaternary 

 might well be abolished, as Primary and Secondary have already 

 been. 



12. I see no sufficient reason for the names Canadian and 

 Trenton as sub-periods. Better divide Ordovician at once into 

 epochs, as you suggest. 



13. I like your schedule of divisions of first and second 

 orders except as regards the Cretaceous and Carboniferous, as 

 already explained. Also, I do not like the term " Azoic," 

 although not prepared to suggest anything better. 



14. I fully endorse your general plan of classification for 

 time and strata. Joseph Le Conte. 



CONTRIBUTION BY G. K. GILBERT. 



So long as historical geology continues to be a living science 

 no definite system of nomenclature can hope to be permanent, 

 nor even, perhaps, to give temporary satisfaction to a majority 

 of geologists. Nevertheless, as intimated by the Journal's cir- 

 cular letter, teachers and geological surveys must have definite 

 systems, and so the task of making and remaking them is a sort 

 of necessary evil. 



