Devonian System in North America. 55 



type is called the " Catskill group " in New York, the " Cadent 

 series" of the Pennsylvania nomenclature. In the eastern 

 Appalachian area this same lithological type of rocks continues 

 all the way upward to the coal measures ; green and red shales, 

 sandstones and conglomerates, and occasionally thin beds of 

 limestone, but with no trace of the marine faunas which char- 

 acterize the interval in Ohio, Indiana, and, particularly, in the 

 interior continental area. In Pennsylvania these rocks have 

 been called " Vespertine Series," " Umbral Series," and " Serai 

 Conglomerates " by the first survey, and " Pocono Sandstone 

 and Conglomerate," " Mauch Chunck Red shale," and " Potts- 

 ville Conglomerate," by the second survey, and in central and 

 eastern Pennsylvania they together reach a maximum thickness 

 of nearly 5,000 feet. These peculiarities, however, do not ex- 

 tend westward of Pennsylvania and New York. Before reach- 

 ing that line, in fact, the red shales have nearly disappeared 

 from the total section, and as the Chemung fauna disappears 

 upward, the new Waverly fauna comes in, but only in the bor- 

 der regions between the two afeas, are found sections in which 

 both the Chemung and the higher Waverly faunas appear. This 

 Waverly fauna is a transitional fauna and is, in the east, gener- 

 ally associated with the higher Sub-carboniferous marine faunas, 

 and in sections in which the next lower fauna is that of the 

 Hamilton or Middle Devonian. In the Eureka faunas described 

 by Mr. Walcott, representatives of it are found in the upper 

 Devonian shales ("White Pine Shales") associated with traces 

 of the upper Devonian faunas of the east. 



The Central Continental Area. 



The central continental area is typically represented in Iowa, 

 Illinois and Missouri, and reaches into Indiana, Kentucky and 

 Tennessee, and possibly far north into British America. 



Its prevailing characteristics are calcareous shales and lime- 

 stones, with some arenaceous admixture at the eastern and south- 

 ern extremities, terminating in black shales, and rarely exceeding 

 two or three hundred feet in thickness. On the north, east 

 and south-east borders of the area the black shale termination 

 is a conspicuous feature, but in the more central portion, in 

 Iowa and Missouri, the black shale is either entirely wanting 

 or but slightly represented. 



In Illinois and Indiana the black shale reaches a thickness of 

 one hundred feet or more, and is immediately followed by the 

 shales and limestone of the Kinderhook, or Knobstone group 

 holding a fauna closely allied with that of the Waverly group 

 of Ohio. East of the Cincinnati axis the black shales are first 

 thin ; they thicken on going eastward, and distinctly represent 

 the upper Devonian of Western New York. Including all that 



