IOWA ACADEMY OF SCIENCES. 63 



and Montgomery counties, the basal formation of the Devonian 

 was regarded as best displayed, and it was then denominated 

 the Callaway limestone. From the typical locality it appears 

 to get thinner northeasterly, and when it reaches the sur- 

 face again, on account of the stratigraphical disturbance in 

 Lincoln and Pike counties, it is not more than twenty-five feet 

 thick. Still farther northward, in the vicinity of Louisiana, it 

 thins out altogether, and at the standard sections at the city 

 itself it is wholly wanting. 



While this formation in the Callaway region presents some 

 differences, it is believed that it is properly paralleled with that 

 of the Cap au Gres region, although in the present connection 

 there is some doubt whether the latter should be properly 

 called the Callaway. In the region under consideration the 

 typical "Western Hamilton" fauna is contained in this forma- 

 tion, the same species that are found farther north in Iowa. 



Grassy Greek Shales. — Immediately beneath the well defined 

 Louisiana limestone, in the vicinity of the town of Louisiana, 

 there are about six feet of black and green shales carrying a 

 characteristically Devonian fish fauna. Ten miles west of 

 Grassy creek, these shales attain a thickness of thirty feet, 

 but southward they thin out completely before the limits of 

 Pike county are reached. 



Louisiana Limestone. — This and the overlying Hannibal shales 

 have long been regarded as forming a portion of the Kinder- 

 hook stage of the Carboniferous. The evidence for now con- 

 sidering these as belonging to the Devonian was given in the 

 volume of the Academy's proceedings published last year. 



