UPPER PALEOZOIC FLORAS 3209 
genera, Lesleya, Megalopteris, and Whittleseya, apparently originated 
in America whence they spread northeastward. ‘The same is true of 
the lower Pottsville Phyllotheca, which appeared a little later in 
Heraclea, and finally, in a new group of forms, became somewhat 
‘characteristic of the Gangamopteris flora of ‘‘Gondwana land.” 
On the whole, therefore, it is probable that the Westphalian flora 
is the joint contribution of the lagoonal—i. e., coal-forming—re- 
gions of western Europe and eastern America. Free inter-com- 
munication was almost certainly by an Arctic land bridge, possibly 
by way of a Greenland-Scandinavian shore connection. ‘The general 
regional distribution of the Pennsylvanian floras is shown in Fig. 1. 
The Stephanian 
Conditions oj deposition and probable equivalents.—The Stephanian 
or Ouralian (including the Gschellian) of Europe dates from the 
Hercynian uplift. Prior to this movement the sea had reached its 
maximum extension in the coalfields of the northern hemisphere. 
The Hercynian thrust caused its practical expulsion from the old 
synclines of western Europe and the creation, especially to the south- 
ward, of new basins, mostly of fresh or brackish water, to which were 
transferred the scenes of coal-formation. In America the line between 
the Westphalian and Stephanian is not yet accurately drawn, the 
fossil floras being not studied in sufficient detail. In view, however, 
of the paleobotanical evidence indicative of a point near the Allegheny- 
Conemaugh boundary, I, personally, am inclined to regard the forma- 
tion of the Mahoning sandstone (conglomeratic), the changed sedi- 
mentation of the Conemaugh formation, the probable upwarp of the 
southern Appalachian region which later resulted in the exclusion of 
the sea from the northern area also, and the consequent climatic 
changes, as due to the same great orogenic influence. Accordingly I 
would provisionally place the greater part, if not all, of the Cone- 
maugh together with the Monongahela in the Stephanian. 
The final exclusion of the sea from the Appalachian trough appears 
to have occurred soon after the deposition of the Ames limestone, near 
the middle of the Conemaugh, since, according to reports, only fresh, 
or possibly brackish water mollusca occur in the higher terranes.* 
tJ. C. White, Report ITA, Geol. Surv. W. Va., p. 622. 
