ON GEOLOGIC TIME-DIVISIONS ZA7 



glomerate lens appears in the Medina formation it can be 

 referred to as the Medina conglomerate lens or episode, without 

 burdening the discussion with a new name, which the conglomer- 

 ate should receive if it be considered a formation. 



2. To that extent which promotes unity of classification 

 without contradiction of fact and no further. In case of doubt 

 whether European standards apply to North American facts, it 

 is better to adopt a North American standard in accordance 

 with the facts. 



3. Palaeozoic era, Palaeozoic system. 



4. Cambrian period, Cambrian group. 



5. Lower Cambrian age, Lower Cambrian series. 



6. Medina epoch, Medina formation. 



7. No. The multiplication of period divisions does not in my 

 judgment tend to the advantage of geologic students. 



8. The absurdity of a double meaning for any term is appar- 

 ent. The usage arises from the effort at excessive subdivision 

 in terms of periods. 



9. and 10. No. This question has been several times con- 

 sidered, and the requirements of the case are adequately met by 

 the use of the terms Comanche age and Comanche series. 



11. Pleistocene, Neocene, Eocene. 



12. I should omit Trenton and Canadian as superfluous. 



13. The proposed scheme contains an undesirable number 

 of period divisions. The sets of facts and corresponding times 

 represented in the scheme by Pliocene, Miocene Comanche, 

 Jurassic, Triassic, Permian, Mississippian, and Ordovician I 

 should transfer from the list of periods to that of ages, where I 

 think they would be adequately represented. 



14. Answered under 1. Bailey Willis. 



CONTRIBUTION BY C. R. KEYES. 



If I understand the questions rightly it would seem more 

 logical to attempt to answer the last one first. 



Uniformity of terminology is the great desideratum of work- 

 ing geologists. The main drawback to the adoption of any 



