IOWA ACADEMY OF SCIENCES. 61 



Folley Limestone. — The name is derived from the little station 

 of Folley, north of Winfield, in Lincoln county, Missouri, 

 where in the west bluffs of the Mississippi river the best expos- 

 ures occur. It crops out on both sides of Sandy creek, south- 

 west of the town, and on the hill-tops south of that stream. 

 There are also good exposures of the limestone on the Illinois 

 side of the river. 



This formation is a light yellow, rather heavily bedded, 

 magnesian limestone, containing few fossils. Locally, thin 

 shale and sandy bands are present. The early Missouri geolo- 

 gists regarded the beds included within the limits of the Folley 

 horizon as representing a part of the first magnesian limestone 

 and all the Trenton. Worthen, on the other hand, referred the 

 beds under consideration to the lower Trenton. 



Bryant Limestone is light blue or gray in color, rather thinly 

 bedded, with more or less numerous shale partings. It is com- 

 pact, somewhat fossiliferous, and presents a marked contrast 

 to both the underlying and overlying dolomitic limestones. 

 The thickness is from 125 to 150 feet. Its most characteristic 

 •exposures are found on Bryant creek, in the northeastern part 

 of Lincoln county, Missouri. It forms the surface rock over a 

 large area north of the fault-line, but to the northward, in 

 Pike county, it becomes gradually covered, first by outliers, 

 and then by the main body of newer layers. In the main, 

 it has close relations with the so-called Trenton of other parts 

 ■of the upper Mississippi valley. 



McGune Limestone. — The upper 25 or 30 feet of what has been 

 heretofore called the Trenton in northeastern Missouri, is a 

 massive, buff, dolomitic limestone, carrying abundant fossils, 

 usually large characteristic forms. The best exposures of the 

 formation are on Peno creek, near McCune station, a dozen 

 miles west of Louisiana, in Pike county, Missouri. It also out- 

 crops in many localities in the southern part of the same 

 county, and in the northern part of Lincoln county, adjoining 

 on the south. 



Buffalo Shales have heretofore been referred to the Hudson, 

 and have been generally considered as the representatives of 

 the Maquoketa shales of northeastern Iowa, and the Cincinnati 

 shales of Ohio. In lithological characters and in fossil con- 

 tents they closely approach these supposed equivalents in the 

 states mentioned, but at the same time they present some very 

 notable differences. It is also somewhat doubtful whether they 



