CHOUTEAU STAGE 279 



Chouteau in central Missouri, many are now known to be from forma- 

 tions other than the terrane under consideration. It is small wonder, 

 therefore, that the Chouteau or Kinderhook fauna as we have long known 

 it is apparently ill defined, anomalous, and puzzling. In the critical 

 study of the lowest Carboniferous faunas of the Mississippi valley there 

 is need, before all else, of exact determinations of the various organic 

 forms from the original Chouteau limestone of central Missouri. It is 

 only with this type fauna that the faunas of the Kinderhook of other 

 localities and other horizons can be with profit compared. Until the 

 fossils from the original Chouteau limestone are carefully collected and 

 studied anew in their entirety, the " Chouteau fauna " must be regarded 

 as a quantity unknown. 



Faunal Relations of the Interval Deposits 

 devonian faunas of the north 



With a single exception, so far as known, the Devonian age of the 

 formations already enumerated in the Iowa section and ending above 

 with the Lime Creek shales has never been questioned. In considering 

 a remarkable fauna at the base of the Chemung, at High Point, New 

 York, Williams * was led to make some comparisons similar to those 

 made sometime earlier by J. M. Clarke f of this fauna with the Lime 

 Creek fauna, in which the latter was considered as having features which 

 were strikingly Carboniferous in aspect. However, after Calvin's demon- 

 stration I that the Lime Creek fauna was typically Devonian for the re- 

 gion, the first-named author was induced to change the views § which 

 he had previously expressed. There is practically no question now but 

 that the Lime Creek beds belong to the Upper Devonian. 



Where the Lime Creek beds are typically developed in Floyd and 

 Cerro Gordo counties, in northern Iowa, Calvin || has shown recently 

 that they are overlain by shaly magnesian limestone carrying Kinder- 

 hook fossils — that is, Chouteau forms. This limestone is very similar to 

 the " Kinderhook " limestone at Le Grand, Iowa, which is believed to be 

 stratigraphically continuous with the Chouteau limestone of central 

 Missouri. 



CHEMUNG FORMATION IN EASTERN IOWA 



The beds in eastern Iowa which were early referred by Hallff to the 



*Am. Jour. Sci. (3), vol. xxv, 1S83, p. 97. 



tU. S. Geol. Survey, Bull. 1G, 1885. 



t Ibid., p. 432. 



g American Geologist, vol. iii, 1889, p. 230. 



|| Iowa Geol. Survey, vol. vii, 1897, p. 144. 



U Geology of Iowa, vol. i, 1858, p. 88. 



