210 Trans. Acad. Set. of St. Louis. 



fications are rather in the nature of approximations, it still 

 must be apparent that the fauna of the Madison limestone 

 has many peculiarities of the earlier Mississippian, and in par- 

 ticular shows a marked affinity throughout with the Kinder- 

 hook fauna." It is recognized by Dr. Girty, however, that 

 it is not a pure Kinderhook fauna with which he is dealing, 

 for he s:tys,* "I do not believe that the facts warrant an 

 exact correlation of the Madison limestone with the Kinder- 

 hook horizon of the Mississippi Basin, although the Kinder- 

 hook affinities of its fauna are obvious. The evidence of such 

 genera as Endothyra, Eumetria, Archimedes, and other forms 

 already mentioned, can not be set aside, and the probabilities 

 involved in placing the Madison limestone, 1,700 feet thick, 

 to offset the 300 feet of shales, sandstones, and limestones of 

 the Kinderhook in the Mississippi Valley, are significant. 



" A more probable interpretation of the facts observed 

 seems to be that the Madison limestone represents a large 

 portion, possibly even the whole, of the Lower Carboniferous 

 period, being a Kinderhook fauna which through uniformity 

 of conditions of environment had maintained its essential 

 characters long after its contemporary fauna to the east had 

 been superseded." 



In making his comparisons between the fauna of the 

 Madison limestone and the Kinderhook fauna, Dr. Girty 

 makes no particular mention of any special division of the 

 Kinderhook faunas, but rather treats them as a unit. A 

 careful examination of his lists of species shows, however, 

 that this relationship is especially with the Chouteau fauna 

 of the Mississippi Valley. The following species of this 

 fauna at Burlington, are present or are represented by closely 

 allied species in the Madison limestone. 



Yellowstone. Burlington. 



Leptaena rhomboidalis Leptaena rhomboidolis 



Orthothetes injiatus Orthothetes inflatus 



Orlhotheles inaequalis Orthothetes inaequalis 



Chonetes ornatus Chonetes logani 



Productella cooperensis Productella concentrica 



* Loc. cit. p. 493. 



