ON GEOLOGIC TIME-DIVISIONS 343 



7. To this proposition I would desire to enter a vigorous 

 protest. Having worked in Kansas, where the Permian is best 

 represented in this country, I can see no good grounds whatever 

 for distinguishing between two groups in respect to which 

 neither the palaeontologist nor the stratigraphist can determine 

 where the one begins and the other ends. Palaeontologically 

 there is nothing of sufficient importance to warrant the division 

 into primary periods. It is true that, so far as we now know, 

 the reptiles began in this time, but every palaeontologist con- 

 fidently expects that they will be found in the true Carboniferous, 

 and in fact they have been found in Kansas in strata that 

 are yet in dispute. Knowing less of the sub-Carboniferous, I 

 cannot give an opinion here, but I do not believe there are 

 any better grounds for division than between the Carboniferous 

 and the Permian. 



Classification of the time periods of the earth must inevita- 

 bly follow the same rules as those applied in the classification 

 of animals and plants, which in the end becomes one of conven- 

 ience, chiefly. If we increase the number of primary divisions, 

 as the tendency seems to be, the number will at last become so 

 large that some future classifier will insist upon reuniting many 

 of them under new and undesirable names. The chief divisions 

 should represent, so far as possible, time periods of equivalent 

 importance, and to say that the Permian period is an equivalent 

 of the Carboniferous, or the Silurian, is certainly incorrect. Per- 

 sonally, I would rather see the Trias annexed to the contiguous 

 divisions ! 



8. I should much prefer to see the name Carboniferous applied 

 to the primary division and distinctive names given to the three 

 subdivisions. There is a very great, almost intolerable, objection 

 to using the name Carboniferous in two senses, or even the Car- 

 bonic and Carboniferous. I very much hope that the name Missis- 

 sippian may be given to the lowest group, some good distinctive 

 term to the intermediate, as Coal Measures, and Permian applied 

 to the uppermost. 



9. For many of the same reasons already given for the 



