FAUNA OF THE LITHOGRAPHIC 55 



Lithologically, the thin sandy layer is more closely related 

 to the underlying shales than with the overlying limestone. 

 Faunally, it has very much nearer affinities with the Western 

 Hamilton (Devonian) than with the Kinderhook (Lower Car- 

 boniferous). In Iowa the " Devonian aspect" of the Kinder- 

 hook faunas has disappeared, largely, since Calvin's recent 

 discovery that the "Chemung" sandstones of Pine creek, in 

 Muscatine county, Iowa, are in reality true Devonian. In Mis- 

 souri the same Devonian facies of the fauna contained in the 

 lowest member of the Carboniferous is lost from view, almost 

 completely, by eliminating the species found in the thin sandy 

 seam at the base of Louisiana or Lithographic limestone. The 

 faunas of the Devonian and Carboniferous of the upper Mis- 

 sissippi valley thus become more sharply contrasted than ever. 

 The apparent mingling of faunas from the two geological sec- 

 tions, manifestly, was based upon erroneous assumptions 

 rather than upon the detailed field evidence. 



Depriving the " Lithographic " limestone, which attains a 

 thickness of more than 60 feet at Louisiana, in Pike county, 

 Missouri, almost entirely of the extensive fauna commonly as- 

 cribed to it, and which, as has been seen, comes from a thin 

 seam lying below the calcareous layer, its geological age be- 

 comes a problem yet to be solved. The few fossils known from 

 the limestone itself have been heretofore rarely met with. It 

 is not at all unlikely that the lower limestone of the Kinder- 

 hook eventually may prove to be of Devonian age. But until 

 abundant evidence to this effect is found, it seems advisable to 

 still consider the Louisiana (Lithographic) limestone as the 

 basal member of the Carboniferous. 



It appears also very probable that a marked unconformity 

 exists between the Carboniferous and Devonian rocks of the 

 area just referred to, instead of a regular sequence of strata 

 as has been usually supposed. The proofs of this statement, 

 however^ are not such at present as to warrant a definite 

 formulation of the evidence ; yet many facts recently obtained 

 point strongly toward this conclusion, while the sharply con- 

 trasted faunal peculiarities are in themselves very suggestive 

 and remarkable. 



