UPPER PALEOZOIC FLORAS 331 
It is probable that the Monongahela was never deposited in the 
southern Appalachian region, from portions of which the Conemaugh 
may also have been absent, the red oxidized sediments of the latter 
being in part derived, I believe, from the eroded unconsolidated older 
Pennsylvanian to the southeastward. 
Floral characters—The Stephanian is marked by the great 
development of Pecopteris, Callipteridium, and Odontopteris of the 
true type. It witnessed the nearly complete disappearance of 
Alethopteris, Sigillaria, and Lepidodendron. Neuropteris of the 
large-pinnuled forms enters its period of decadence. Before its close 
appear the first representatives of Callipteris, Walchia, Taeniopteris 
of the simple type, Pterophyllum, Zamites, and Plagiozamites, all 
characteristic of the Permian or later periods. 
In eastern America, where the relations of land and water were but 
gradually altered and the sedimentation was continuous, the passage 
to the Stephanian flora has no line of sharp paleobotanical demarka- 
tion. ‘The change appears to be gentle and the older forms drop out 
more slowly. In Europe, on the other hand, the contrast is a little 
sharper; the old types disappear more abruptly and many new ones 
take their places. A number of these new types have not yet been 
found in the Permian of this country. Among these are the four 
Permian coniferal and cycadalean genera above mentioned. 
Source and distribution of the flora.—tit is clear that the new ele- 
ments of our Stephanian flora are chiefly, at least, of European origin, 
the plant life there having been directly influenced by the important 
physical changes to which it was immediately subjected. The various 
exotic types migrated to North America, probably, along or near the 
general route traversed by their Westphalian predecessors. Also, 
since the Stephanian flora of the American basins seems to afford no 
evidence of a rapid or strongly pronounced climatic alteration, it 
becomes fairly probable that the more abrupt plant changes described 
in western Europe were induced chiefly by the sweeping orogenic 
effects of the Hercynian movement, rather than by a great climatic 
change of world-wide extent. This does not, however, preclude a 
moderate but far-reaching modification of climate, in which changes 
in the atmospheric composition may have played a subtle if not 
important part. It seems hardly possible that the tremendous 
