70 UNIVERSITY OF MISSOURI BULLETIN 



shales are to be correlated with the upper part of the Devonian 

 of Iowa, but whether the shales at Louisiana are merely a 

 near shore phase of them or belong to a higher formation, or 

 were separated from them by a barrier while they were forming 

 remains to be investigated. The invertebrate fauna suggests 

 the former as a possibility but arthrodires occur in the Lou- 

 isiana region and have never been found in the Craghead Creek 

 shales. As they swam freely and were not restricted by shal- 

 low or deep water, they should occur in both faunas, if they 

 are contemporaneous and not separated by a barrier. 



Twenty miles west of Fulton the Devonian consists of 

 a limestone twelve to twenty feet in thickness, which is not 

 abundantly fossiliferous, and in which the main forms present 

 are corals and Pleurotomaria providencis, which also occurs 

 in the Callaway limestone near Fulton. This limestone appears 

 along the bluffs of the Missouri river and the exposures are 

 good on account of railway excavations. The exposure is 

 seven or eight miles long, running from Providence to near 

 Hartsburg. About two miles below Providence another De- 

 vonian limestone wedges in unconformably on top of the first 

 but is present for only three or four hundred feet. It is abund- 

 antly fossiliferous but as the fossils are mainly A try pa reti- 

 cularis the data are insufficient for correlation. The bed 

 seems to correspond to one of the A try pa reticularis horizons of 

 the Callaway limestone twenty miles east. The limestone 

 ranges from one inch to four feet in thickness. At the same 

 place a shale that runs for more than one thousand feet wedges 

 in unconformably on top of both limestones. It is less than 

 four feet in thickness and occurs at only the one place in the 

 exposures along the river. In most cases both the top and the 

 bottom of the Devonian are exposed along the bluffs and the 

 absence of the second limestone and the overlying shale is 

 demonstrated. The shale is probably nonmarine, as it con- 

 tains great numbers of fragments of plants and no other fossils. 



These beds have not been named or correlated further 

 then Ulrich's reference to Middle and Upper Devonian of 

 beds of a similar nature that occur in the bluffs on the other 



