CLASSIFICATION OF THE MISSISSIPPIAN SERIES. 



Because of its vast array of finely preserved fossil forms, the 

 Mississippian or Lower Carboniferous limestone series, has, since 

 the beginning of geologic investigation in the Mississippi valley, 

 aroused great interest. At an early date the fossils of the suc- 

 cessive beds were studied, and were illustrated in the geological 

 reports of Iowa, Illinois, and Missouri, and formation names were 

 given to the various strata. In the final adjustment of the work 

 of all the earlier investigators, the following formation names, 

 from the base upward, came to be recognized, (i) Kinderhook, 

 (2) Burlington, (3) Keokuk, (4) Warsaw, (5) St. Louis, and 

 (6) Kaskaskia or Chester. Each one of these divisions was 

 held to be of equal importance with all the others, essentially, 

 and until recently this original, more or less artificial, classifica- 

 tion remained in vogue. 



The true classification of rock strata and fossil faunas is but 

 an incident in the elaboration of the geologic history of a 

 region, and in order to make a natural classification of these 

 phenomena, they must be considered from a historical stand- 

 point. The classifications of rock strata which have been gen- 

 erally used, are based upon two distinct sets of criteria, (1) 

 stratigraphic, and (2) faunal. A stratigraphic classification by 

 no means excludes the fossil evidence, and is based fully as 

 much upon the differences observed among the fossil species of 

 successive formations as upon the physical characteristics of the 

 strata; but the fossils are looked upon in the same light as the 

 physical characters, as a sort of label of the strata, rather than 

 as a real life element subject to all the laws of organisms. The 

 old classification of the Mississippian series into the six forma- 

 tions indicated above was purely stratigraphic in its nature, 

 although great stress was laid upon the fossil contents of the 

 various formations. 



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