the Coal-fields of Pennsylvania. 413 



anthracite basins in their fossils, that Mr. Lesquereux already 

 recognizes more than twenty familiar European species as 

 common to these once continuously united coal-fields. It has 

 been indicated above, that the two different groups of the coal 

 strata of Pennsylvania, the lower or white ash, and the upper 

 or red ash, are characterized by somewhat different species, 

 though these more or less intermingle. Satisfied of this fact, 

 of a general prevalence of certain forms in certain parts of the 

 coal-measures, we have aimed at carrying our inquiry a step 

 farther, to ascertain whether or not any or all of the individual 

 coal-seams themselves are separately recognizable by their fossil 

 plants. Undoubtedly, in some of the broadly deposited and 

 uniformly conditioned coal-beds and coal-slates of the western 

 bituminous coal-fields, we do observe a most striking preva* 

 lence of the same species within the same layer, on compara- 

 tively wide areas ; but amid the more irregularly accumu- 

 lated beds, of especially the lower or white ash anthra- 

 cite strata, formed on a less stable portion of the nowhere 

 absolutely stationary crust, the inconstancy in the vegetation 

 of even the same coal-seam is, for the most part, if not even 

 quite, too great to permit us to attempt to identify it by its 

 fossils merely. Again, in some instances, coal-beds which are 

 demonstrably different, are almost absolutely identical in their 

 fossils. This is the case with the "Gate" and "Salem" 

 coals, near Pottsville. So strikingly alike are they in their 

 vegetation, that Mr. Lesquereux strongly inclines to regard 

 them as but the detached parts of originally one sheet of coal, 

 and to suspect that there is some error of obscurity in my sec- 

 tion, which shows them to be separated by several hundred 

 feet of strata, including a number of beds of coal. Of the 

 validity of the proofs, showing the so-called Salem vein, to be 

 different coal from the Gate vein, and several stages higher in 

 the series, there cannot, however, be any question, and the 

 palaeontological evidence for identity must give way before the 

 higher and decisive demonstration from superposition, of their 

 difference in age. 



