FERNS, FOSSILS AND FUEL 
from Mississippian times in America, and from the Kulm, 
which corresponds in Europe to the Mississippian. The 
flora represents a more or less intermediary stage between 
that of the Devonian and that of the Pennsylvanian 
period which follows it. 
During Pennsylvanian times, vegetation flourished 
luxuriantly, and the great beds of bituminous and anthra¬ 
cite coal of North America were formed. The best coal 
seams of Europe and Asia also belong to this period. 
The name Pennsylvanian is given to the coal age in 
this country because the type formations, where the geol¬ 
ogy of the period was first studied on this continent, are 
in Pennsylvania. A type formation is a local deposit 
after which a geologic horizon is named, because the 
rocks that were formed during it were first studied in that 
particular place. The older Pennsylvanian in America 
corresponds in Europe to the Westphalian whose type 
formations were first studied near Westphalia in Ger¬ 
many. The younger Pennsylvanian in this country is 
the same as the Stephanian in Europe, whose type for¬ 
mation is near St. Etienne in France. 
In Russia, the formations of the great coal age were 
first studied in the deposits near Moscow and in the 
Ural Mountains. The following tabulation shows this 
correlation of the Pennsylvanian of North America 
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