66 GEOLOGICAL FORMATIONS 



( 2 ) That the fauna is the typical fauna of the Kinderhook 

 shales. 



(3) There are mingled in this fauna some of the forms 

 found both above and below, which are there associated with 

 species characteristic of the lower Burlington limestone. 



Here, then, is a well-defined Kinderhook fauna intercalated 

 in the Burlington limestone, with practically no change of litho- 

 logical characters ; a lower fauna suddenly appearing in the 

 midst of a higher. This is the most marked instance of the 

 kind that is at present known in the Carboniferous of the 

 Mississippi valley. Though the separation is not very great, 

 the present case is a striking illustration of Barrande's cele- 

 brated Doctrine of Colonies, so clearly developed in his Sys- 

 tem Silurien du Centre de la Boheme,* and so ably defined in 

 his Defense des Colonies. 



It is not to be inferred, however, that during the short 

 supremacy of the lower fauna, in the midst of an upper, there 

 was a complete extinction of the deposed forms, but rather, 

 that owing to peculiar conditions the lower fauna merely dis- 

 placed the upper temporarily, or pushed it aside into other 

 districts for the time being. 



As far south as Ste. Genevieve county the Burlington beds 

 still preserve their characteristic integrity. In the central part 

 of the State the formation is well exposed in at least eight or 

 ten counties. It forms the surface rock at and around Sedalia. 

 In the northern part of Morgan county numerous small out- 

 liers ol this rock are found on the highest hill-tops, resting 

 directly upon the Ozark series. On the Osage river it is well 

 developed, resting upon a thin layer of Chouteau, and this, 

 again, upon the old Magnesian limestones. Southwestward 

 from the last locality the Augusta group has not, as yet, re- 

 ceived very much detailed study, except in Greene county, 

 where, as already mentioned, the Burlington is well defined in 

 all its characteristic peculiarities. 



Keokuk Limestone, — The upper member of the Augusta has 

 its distribution chiefly on the eastern side of the " Father of 



*Vol. I, p. 73. 1852. 



