250 REPORT OF THE AMERICAN COMMITTEE. 
been recognized tentatively at several localities within the In- 
terior Basin. If those identifications prove exact, the base will 
be well-defined throughout. 
At the top of the Upper Coal Measures in Pennsylvania, Ohio, 
and West Virginia, are the beds characterized by a flora con- 
taining many Permian forms. These form the Upper Barren 
Group as given in the table of synonyms. At not far from the 
same position, apparently, are the beds in Illinois, Texas, and New 
Mexico, containing reptilian types, which in Europe belong ex- 
clusively to the Permian. 
The presence of these forms justly leads us to believe that in 
America the rocks of the Carbonic represent in full the whole 
series of Carbonic as found in Europe, and justifies us in giving 
to the upper part of the Upper Carbonic the name of Permo- 
Carbonic. At the same time this subdivision must be taken 
only as a part of the Upper Coal Measures and not as rank- 
ing equally with it; for the conditions of marine life remain 
practically the same throughout the whole of the Coal Meas- 
ures ; there being identical forms of fish-life in the upper beds of 
the Appalachian and of the Interior Basin ; while in the latter, 
as well as in New Mexico and farther west, there is at the top of 
the column a commingling of Coal Measure forms with a few 
types which characterize the Permian in Europe. It is suffi- 
ciently evident, then, that while the whole of Carboniferous time 
is represented by deposits in America, there was no such change 
in conditions as to produce a Permian period or system such as 
occurs in portions of Europe. 
A notable change occurred at the beginning of the Upper Coal 
Measures which aifected vegetable life, for above the Pittsburgh 
coal-bed, Lepidodendron and SigiUaria became exceedingly rare, 
and at most localities they are wholly wanting. 
Middle Coal Measures. 
Synonyms. 
Pennsylvania XIII. in part. | Lower Barren Group. f XIV. 
Allegheny Elver Series. [ Lower Productive Group. | XIII. 
..... f XIV. 1 
\ irginia. \ xiTT 1 ^i^^^^ Coal Measures. 
Qj • f Barren Measures. 
1 Lower Coal Measures in part. 
