STIGMARIA. 
133 
shire^ and he detected them in the United 
States under the coal seams of the anthra- 
cite regions of Pottsville Wyoming, and 
Wilkesbarre, on the Susquehanna. Dr. 
Rogers informed him that they were discov¬ 
ered in the same position in the continuation 
of the coal district in Virginia. Mr. Logan 
afterwards observed them in a similar posi¬ 
tion in the coal country of Nova Scotia. 
Mr. Lyell, who has devoted much attention 
to, and carefully examined the underclays of 
the American coal fields, points out their 
common occurrence in that part of the 
world beneath the coal beds, so that 
some very general conditions must have 
produced those beds over so large a portion 
of the earth’s surface, conditions with which 
the production of the coal itself would 
appear to be connected.”* 
“ The remains of Stigmaria are so abun¬ 
dant throughout the whole of the carbonif¬ 
erous formation, that it is impossible to 
travel far along any road, without its form 
being detected by the practised eye. In 
* Page 147. 
M 
