

willtams.] JAMES HALL, S. S. LYON. 155 



In 1859 1 James Hall presented his view of the relation of the strata 

 of the Mississippi Valley to those of the New York section. The inter- 

 val between the Cheinuug and the Coal Measures of the Appalachian 

 section is filled, in the West, by the representatives of the Carboniferous 

 limestone. The following table explains this view : 2 



New York and Pennsylvania Mississippi Valley Coal Measures. 



Coal Measures. 



f Kaskaskia limestone. 



Red shales ^| Great Carboniferous lime- | Ferrnginona sandstone. 



Conglomerate )> stones of the Mississippi^ ?,? ^ouis limestone. 



Catskill Mountain group. . J Valley. ] Warsaw limestone. 



to r ' J Keokuk limestone. 



^Burlington limestone. 



Chemung and Portage groups Chemung and Portage groups. 



Hamilton group Hamilton group. 



Concerning the fauna of the Western rocks, which he regarded as the 

 equivalent of the Chemung and Portage groups, he reported that he had 

 traced the rocks through Ohio, and then from Indiana into Michigan, 

 across Indiana and Illinois to Iowa, and into Missouri. He recognized 

 scarcely a single species identical, but found representative forms. 



It will be seen thus that the dominant means of correlation was the 

 strata, probably the black shale and the argillaceous and arenaceous 

 deposits following below the limestone. The suggestion was thrown 

 out that the cause of the great difference in sedimentation is the eleva- 

 tion of the Cincinnati axis, allowing a sea to be depositing calcareous 

 sediments in the Mississippi Valley, while a coarse deposit was being 

 made east of that axis. 3 This is evidently the true explanation. 



It was the wide territory which American geologists had to study 

 which led them to recognize the great difference in the conditions which 

 existed at the same geological time in separate regions of the continent, 

 and developed that minute comparative study of fossils which alone 

 has made exact correlation possible. 



In the above table it is evideut that up to this time Professor Hall 

 still held to the view that the Chemung Group of Iowa, Missouri, and 

 Illinois was, as he called it, " Subcarboniferous," that is, was below 

 the " Carboniferous formations," not one of them. 



In 1860 Sydney S. Lyon 4 recognized three divisions, viz: "(1) Coal 

 Measures, (2) Millstone grit series, (3) Subcarboniferous series f but 

 in the latter, the lower or " Subcarboniferous series," he follows the 

 erroneous usage introduced by Owen, for we find included under this 

 division not only the lower Carboniferous rocks, but all from the "Black 

 slate " to the " Catenipora beds," inclusive. " Subcarboniferous series" 

 applied to the rocks below the Millstone grit is a modification of Dr. 

 Owen's usage. Owen proposed the name " Subcarboniferous limestone," 

 but applied it in about the same sense in which Mr. Lyon applied the 

 name " Subcarboniferous series." Mr. Lyon restricted the use of the 



1 Paleontology of New York, vol. 3. a Ibid., p. 53. 8 Ibid., p. 58. 



•Discussion of the Stratigraphical Arrangement of the Rocks of Kentucky. Trans. St. Louis Acad. 

 Soi., vol. 1, 1860, pp. 612-621. 



