232 REPORT OF THE AMERICAN COMMITTEE. 
interval in Ohio, Indiana, and particularly in the interior conti- 
nental area. In Pennsylvania these rocks have been called 
"Vespertine Series," " Urabral Series," and " Serai Conglomer- 
ates" by the first survey, and " Pocono Sandstone and Conglom- 
erate," "Mauch Chunk Red shale," and " Pottsville Con- 
glomerate " by the second survey, and in central and eastern 
Pennsylvania they together reach a maximum thickness of nearly 
5000 feet. These peculiarities, however, do not extend westward 
of Pennsylvania "and New York. Before reaching 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 border regions between the two 
areas, are found sections in which both the Chemung and the 
higher Waverly faunas appear. This Waverly fauna is a transi- 
tional fauna and is, in the east, generally associated with the 
higher Sub-carboniferous marine faunas, and in sections in which 
the next lower fauna is that of the Hamilton series or Middle 
Devonian. In the Eureka faunas described by Mr. AValcott, 
representatives of it are found in the upper Devonian shales 
(" White Pine Shales ") associated with traces of the upper De- 
vonian 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 
southeast 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 limestones of the Kinderhook, or Knobstone stage 
holding a fauna closely allied with that of the Waverly stage 
of Ohio. East of the Cincinnati axis the black shales are first 
thin ; they thicken on going eastward, and distinctly represent 
