154 THE DEVONIAN AND CARBONIFEROUS. [bull. 80. 



the general relations of oceans and continents remained substantially 

 the same. When, however, the attempt is made to trace the subdivi- 

 sions and to correlate series and stages and the lesser zones of the geo- 

 logical classifications by lithologic means, then the inadequacy of the 

 method becomes apparent. As we look over the history of the work of 

 geologists in America, we find the majority, and for the field I have 

 specially studied I am inclined to say nearly all, of the erroneous cor- 

 relations are directly traceable to a too great dependence upon lithology. 

 The following exhibits the classification of the Carboniferous lime- 

 stone of Iowa, Illinois, and Missouri as it was understood by Hall in 

 1858. 1 



COAL MEASURES OF IOWA, ILLINOIS, AND MISSOURI. 



VI. Kaskaskia limestone or Upper Archi- ) Kagka8kia and Cne8 ter, Illinois. St. 

 raeclea limestone. Pentremital lime- > Mary's Missouri, 

 stone. j 



Lower arenaceous beds of passage. 

 V. Gray, brown, and ferruginous sandstone ) Below Ste. Genevieve, Missouri. Below 

 overlying limestone of St. Louis and > Prairie du Rocher and Kaskaskia, 

 Alton. ) Illinois. 



Abrupt passage. 

 IV. St. Louis limestone, Concretionary /Highest beds below Keokuk, Alton, St. 

 limestone. $ Louis, Ste. Genevieve, Prairie du Rocher. 



Passage arenaceous or indistinct. 



III. Arenaceous bed, Keokuk and north-'" 

 ward. Warsaw limestone or Second 



Warsaw and Alton, Illinois. Blooming- 



ward. Warsaw limestone or feecona i ton and Spurgen Hill, Indiana. Opposite 

 Archimedes limestone. Magnesian ( Fort Madi * Mount Pleasant, 

 limestone. 

 Passage soft, marly, geodiferous. Geode bed, Keokuk, Nashville, Iowa, and 

 Warsaw, Illinois. 



II. Keokuk limestone Lower Archimedes ) Keokuk and Mount Pleasant, Iowa. 

 limestone Archimedes limestone, > Q uincy , Illinois. Hannibal, Missouri. 

 Owen and Swallow. ) 



_ .. ™^inn*w $ Rapids above Keokuk, Iowa. Quincy, 



Passage cherty limestone, 60 to 100 feet. I Illinois. 



„.,.,. S Burlington, Iowa, Quincy, Illinois, Han- 



I. Burlington limestone J nibal> Missouri. 



Oolitic limestone, sandstone, and shale of ) Burlington and Evan8 Falls, Iowa. Han- 

 Chemung and Portage groups of New > Qiba f Missouri, etc . 

 York. ; 



Iii 1859 Mr. A. H. Worthen 1 reported the discovery of a terrestrial 

 flora in the Chester limestone group. 



While constructing a section of the Ohio Bluffs he discovered, in 1851, 

 in the middle of the Chester limestone of Pope County, a bed of cal- 

 careo- argillaceous material containing fossil plants. The flora does 

 not present a single species in common with the Carboniferous. Among 

 the plants he fouud representatives of the genera Stigmaria, Sigillaria, 

 Knorria, and Lepidodendra, but of species quite distinct from those in 

 the Coal Measures. 



" This fact seems to indicate the close proximity of an ancient coast 

 line in this direction," and its probability is increased by the fact that 

 "the Subcarboniferous series thins out rapidly to the north and east." 



1 Geology of Iowa, p. 109. 



1 Worthen, A. H : Remarks on the discovery of a terrestrial flora in the Mountain limestone of 

 Illinois. Am. Assoc, Proc., vol. 13, 1859, pp. 312, 313. 



