FOSSIL PLANTS. 
505 
with coal No. 2. Hymenophyllites furcatus has more generally been found be¬ 
low the Millstone grit, but it ascends, though rarely, to coal No. 2, where also 
Hymenophyllites splendens, H. Schlotheimii and some other species of the section 
Aphlebia are generally found. 
As representative of the higher coal strata of Illinois, or of coal No. 5, there 
is no particular species to quote. Alethopteris aquilina, with Pecopteris unita, P. 
plumosa , Gordaites angustifolia, and species of Lepidophloios, are there repre¬ 
sented by more abundant specimens than anywhere else, but remains of these 
plants have been also observed in the lower Coal Measures. In the anthracite 
basin of Pennsylvania, the highest strata are recognized by the presence of 
Pecopteris arborescens, which has not been as yet positively discovered in Illi¬ 
nois, the small specimens referred to it from a nodule of Mazon creek being 
too obscure for certain identification. This species, the most abundant of all 
in some localities of Pennsylvania, is found also in profusion in the red clay 
beds of Ohio, especially in the grotto of flowers , near Marietta, where it is 
represented by a slightly different form, perhaps a mere variety of P. rubra , 
Lesqx. In Europe, it ascends to the Permian, where its characters, though 
somewhat modified, have been considered as specific by Goppert, who has 
named it P. ( Cyatheites ) Sclilotlieimii. It is there, as with us, associated with 
its large form P. Cyathea, Brgt. The section Cyatheites of the genus Pecopte¬ 
ris, is, indeed, of all the fossil ferns of the coal, the one which is, in some of 
its species, characteristic of the higher coal strata. But as yet these species 
are indifferently known, and therefore it is hardly possible to indicate them as 
peculiar to a certain horizon. For example, Pecopteris polymorpha , Brgt., 
abounds in the highest coal strata of Illinois at Grayville, and near New Har¬ 
mony, lnd. It is generally like P. arborescens, a marked species of our upper 
Coal Measures, while Pecopteris abbreviata, which Prof. Geinitz takes as a 
mere variety of it, is common at Morris, Mazon creek and other places, always 
in connection with coal No. 2, and has not yet been observed in higher strata. 
The differences in these horizons, as well as in the form of the pinnae, indicate 
these remains as representing two different species, though the nervation is of 
the same kind. It is certain that, as the Lycopodiaceous plants of the coal 
decrease in the number of their representatives, as in their size, in ascending 
in the Coal Measures, they are proportionally replaced by ferns, either herba¬ 
ceous or arborescent. This change is everywhere evident in the shale over¬ 
laying the coal beds, as in the coal itself. At Grayville, and especially at 
Springfield, Ill., where the upper coal is nearly 200 feet above coal No. 5, 
the lamellae of.the coal bear a quantity of recognizable leaflets and branches 
of ferns, especially of the genus Pecopteris. The roof shales of the Pomroy 
coal in Ohio are thickly covered with remains of ferns, especially large'pinnae, 
still bearing leaves of Neuropteris flexuosa and N. hirsuta. A bed of shale, 
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