20 PALEONTOLOGY OF KENTUCKY. 



be doubted, when we find the many knobs by which it is covered capped with 

 the Carboniferous formation. Those knobs can not be the products of volcanic 

 action. The undisturbed horizontality of their layers proves them to be the 

 result of denudation. The denuding influence of heat, frost and rain appears 

 to be too insignificant to have produced such an amount of excavation as would 

 have been necessary to cut down many square miles of land from their former 

 to their present level a difference in some places amounting to several hundred 

 feet. However, we must always bear in mind that geological agencies are 

 enabled to do their enormous work, not so much by their magnitude, but 

 mainly by their perseverance throughout the endless spaces of geological 

 times. 



Of the Subcarboniferous we distinguish the following five subdivisions : Kin- 

 derhook, Burlington, Keokuk, St. Louis and Chester groups. It is doubtfu 

 whether the Kinderhook group is really different from the Chemung group, 

 and, even if a difference exists, it remains questionable where to place it prop- 

 erly, whether with the Devonian or the Subcarboniferous ; its fossils show a 

 nearer relationship to the Devonian fauna than to that of the superimposed 

 strata of the Subcarboniferous. In Kentucky we find only the three younger 

 formations, viz. ; the Keokuk, the St. Louis and the Chester, which form a 

 kind of border around the coal fields. The St. Louis limestone gives a peculiar 

 feature to the country of which it forms the surface-rock. In its strata we 

 find the many, often very extensive caverns, and the surface covered over 

 with numerous funnel-shaped sink-holes. All the formations and groups so 

 far enumerated, originated during the Palaeozoic Period ; they alone are of 

 interest to Kentucky, inasmuch as they embrace all the surface-rocks of our 

 State. 



MESOZOIC AGE. This produced the following three groups : Triassic, Jurassic 

 and Cretaceous. None of these are represented in our State, though they 

 cover vast areas of our continent, especially the Triassic and Cretaceous, whilst 

 the Jurassic is only recognized in the Rocky Mountains and on its western 

 slope. 



CENOZOIC AGE. During this age, which reaches to the present time, the 

 Tertiary formation was called into existence. In it we find the earliest repre- 

 sentatives of the different genera and species of animals and plants which to- 

 day inhabit our planet. The subdivisions of the Tertiary are Eocene, Miocene 

 and Pliocene. 



Of living or recent species, the Eocene contains 3 to 4 per cent. ; the Miocene 

 from 18 to 20 per cent., and the Pliocene from 35 to 95 per cent, according to 

 Ly ell's definition of these different groups. 



In the localities where Lyell studied these different rocks, there was a clear 



