160 THE DEVONIAN AND CARBONIFEROUS. [bull. 80. 



systems, aud for the Carboniferous system the nomenclature already 

 proposed in the Missouri (1855) and Iowa (1858) Reports was adopted 

 with some modifications. 1 



In classifying the Carboniferous rocks, Worthen included the " Barren 

 Coal Measures" or "Millstone grit" in the Coal Measures. They are 

 seen in the southern part of the State, but not in the more northern 

 part, where the Coal Measures proper or " Upper Coal Measures n out- 

 crop. They are terminated by a sandstone called the "Anvil rock 

 sandstone " (Owen), upon which are some limestones regarded as equiva- 

 lent to the " Great limestone of Pennsylvania.' 72 



Worthen adopted the name " Subcarboniferous limestone" for the 

 rocks between the Black slate and the Coal Measures and Conglom- 

 erate. 



The following expresses the classification of the upper Paleozoic 



rocks of Illinois as interpreted by Mr. Worthen in 1866 : 3 



. 



Coal Measures and Millstone grit.. .Coal Measures, 600-1,200 feet aud Conglomerate. 



f Chester group, 500-800 feet. 



| St. Louis group, 50-200 feet. 

 Subcarboniferous \ Keokuk group, 100-150 feet. 



| Burlington limestone, 25-200 feet. 



^Kiuderhook group, 100-150 feet. 



( Black slate, 10-60 feet. 

 Devonian ■ < Devonian limestone, 10-120 feot. 



( Oriskany sandstone, 40-60 feet. 

 Devonian aud Silurian Clear Creek limestone. 



Mr. Worthen in the first report considered the u Clear Creek lime- 

 stone as equivalent, in its upper part, to the base of the Devonian. The 

 name "Chester group" is proposed by Worthen for the "Chester lime- 

 stone" aud the underlying " Ferruginous sandstone" of the Missouri 

 Keports. The "Warsaw limestone" (Hall) of the Iowa Report, Mr. 

 Worthen united with the " St. Louis limestone" of Missouri to form the 

 " St. Louis group." He also united the tl Geode bed," the " Keokuk 

 limestone," aud the underlying "Cherty beds" of the Iowa Eeport to 

 constitute his " Keokuk group." The " Siliceous group " of Tennessee 

 and Alabama he regarded as a southern extension of this same " Keo- 

 kuk group" of Illinois. The author further pointed out the fact that 

 the— 



Subcarboniferous limestone becomes arenaceous on the northeastern border of the 

 coal field, and that all the upper members above the Kinderhook group thin out in 

 that direction, and are replaced by the grit stones forming the lowest member of the 

 series ; and in Ohio these grit stones occupy the entire horizon from the Conglomer- 

 ate to the " Black slate." 4 



The name "Burlington limestone" was adopted with substantially 

 its original meaning as applied by Hall in the typical locality, Burling- 

 ton, Iowa. It was not recognized outside the States of Iowa, Illinois, 

 and Missouri. It is famous for the great abundance of crinoids, which 

 are found in beautiful preservation about Burlington. 



1 Seo Geol. Survey of 111., vol. ], p, 40. s Ibid., vol. 1, p. 26. 



2 Ibid., p. 61, et seq. * Ibid. , p. 101. 



