ON GEOLOGIC TIME-DIVISIONS 337 



Mesozoic 



f Cretaceous (Upper) 

 J Comanche (Lower Cretaceous) 

 | Jurassic 

 I^Triassic 



[Termian 

 I Carboniferous 



I Mississippian (sub-Carboniferous) 

 Palaeozoic - -{ Devonian 



Silurian 



Ordovician 



Cambrian 



( Keweenawan 

 Proterozoic - - -j Upper Huronian 

 ( Lower Huronian 



Azoic - - Archaean 



14. What would you say to this plan of classification : 



Era - - - Group 



Period - - System 



Epoch - - Series 



Stasre - . - - Formation 



CONTRIBUTION BY JOSEPH LE CONTE. 



I hereby give answers to your questions as briefly as possi- 

 ble : 



1. I am not prepared to go further than divisions of the 

 second order. 



2. European standards, as first in the field, must be followed 

 as far as possible, but should be modified, if necessary. But 

 eventually we must have a world standard, at least for divisions 

 of first and second orders. 



3. I think — Era and Group are best. 



4. " " Period and System are best. 



5. " " Epoch and Series are best. 



6. " " Stage and Formation are best. 



7. [a) Sub- Carboniferous is certainly coordinate with Car- 

 boniferous proper, but I do not think that Permian is. Witness 

 the tendency to unite Carboniferous and Permian under Permo- 

 Carboniferous. 



