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of which may eventually perhaps be referred to the Lower Carboniferous. 

 From a paleobotanic standpoint the Pottsville formation is the beginning of 

 Mesocarboniferous. 



Briefly stated, the following are some of the general conclusions 

 reached : 



No evidence of a marked or general unconformity between the 

 Pottsville and Mauch Chunk is noticeable in this region, though at 

 various points within several hundred feet of the strata beds of small 

 bowlders or coarse conglomerates are imposed, in knife-edge contact, 

 on the distinctly uneven surfaces of olive-green mud-beds. 



The flora in the roof of the Buck Mountain coal, or its supposed 

 equivalents, at the base of the Lower Coal-measures at Pottsville is a 

 typical Coal-measures flora, very distinct from the floras typical of the 

 Pottsville formation. 



The fossil plants of the Pottsville formation in the type region 

 exhibit a rapid development and series of changes or modifications, 

 which, if treated with great systematic refinement, are of high strati- 

 graphic value. With the exception of the species from the topmost 

 beds of the formation, the ferns are, in general, readily distinguished 

 specifically from those at the base of the Lower Coal-measures, or 

 Alleghany series, as recognized in the northern United States, while 

 the floras of the lower portions of the section are found, in passing 

 downward, to bear still less resemblance to those of the Lower Coal- 

 measures. Two principal divisions of the formation, to which com- 

 paratively few fern species are common, are recognized. These divi- 

 sions, which coincide with the natural grouping of the Lykens coals, 

 are here termed the Lower Lykens division and the Upper Lykens 

 division. A portion, including about two hundred feet of the type 

 section between these two paleontologic divisions, contains a mixed 

 flora, and has been temporarily designated the Lower Intermediate 

 division. 



Further paleontologic study of the Pottsville formation appears to 

 fully confirm the earlier conclusion, based on the examination of the 

 plants, that the thinner sections of the formation along the northern 

 and western borders of the Appalachian trough do not contain beds 

 as old as those in the lower portion of the thick sections along the 

 eastern border, e. g., in the Schuylkill and Great Flat Top regions. 

 The positions of the respective floras in the sections plainly indicate 

 a transgression of the sea toward the north and west during Pottsville 

 time. 



