176 W. C. MORSE AND A. F. FOERSTE 
Berea. This is a strong argument, yet from facts set forth above it 
seems advisable to refer the rapidly decreasing horizon to the Bedford- 
Berea. 
In this connection, it might be well to give the conclusions reached 
by Professor Williams ia his paleontolenics study of the black shales. 
He states that an 
examination of the sections at Irvine, Kentucky, the other side of the Cumberland 
channel revealed the fact that there the black shales were thinner but held on in 
their purity, well up into Carboniferous time. The intercalations consist of 
calcareous and ferruginous, concretionary sheets, and carry undoubted Carbonif- 
erous fossils and occur in the sections before the black shale loses its characteristic 
expression. ? 
These black shales have been correlated with the Ohio black shale 
in the various geological reports of the state. The geologists of the 
National Survey, approaching the field from the south, have, on the 
other hand, designated them as the Chattanooga shale.? Both have 
referred them, in their entirety, to the Devonian system. That they 
belong to both the Devonian and Carboniferous systems has, it is 
thought, been clearly demonstrated. 
Of the London and Richmond Folios of the U. S. Geological Sur- 
vey, the latter adjoins the Irvine field. In these Campbell has desig- 
nated the clay shales and argillaceous sandstones, above the Black 
shale, as the Waverly formation. It is permissible, according to the 
rules of that survey, to reduce a series to the rank of a formation, but, 
as applied here, Waverly covers not more than the upper half of that 
division. The lower half, Bedford, Berea, and Sunbury, has just been 
shown to be included within the limits of the Chattanooga (Ohio) 
shale. 
It is interesting to note that Professor Grabau anticipated this 
limitation. Referring to the London Folio, he states that: 
The shale above the Black (Ohio) shale is referred to the Waverly, of which 
it probably constitutes the upper portion only. As at Irvine, the transition from 
the Black shale to the overlying beds is probably a gradual one.3 
This conclusion seems to have been reached deductively, from a 
t Am. Jour. Sci., 4th series, Vol. III, p. 3098. 
2 Estillville, London and Richmond Folios, U. S. Geol. Surv. 
3 Bull. Geol. Soc. Am., Vol. XVII, pp. 609, 610. 
