316 BOTANY AND PALEONTOLOGY 



tinction of another name (that of false coal-measures), as if they were a 

 peculiar formation. The proportion of large species and fossil trees ap- 

 pears to be greater in Arkansas. But the same proportion continues, 

 though in decreasing order, till we reach coal No. 1 A and coal No. 1 B 

 above the Millstone Grit. And certainly the difference in the species 

 between these last strata and coal No. 4 placed at the base of the Maho- 

 ning Sandstone, at a distance of about 250 feet, more or less, would appear 

 far greater than between the Subconglomerate coal of Arkansas and coal 

 No. 1 B. 



New discoveries of fossil plants by the Geological State Survey of 

 Illinois show the proportion of large trees increasing as far down as below 

 the Upper Archimedes Limestone, where a thin bed of coal is sometimes 

 present, as at Fayetteville. Nevertheless, the plants of this low position 

 are still of the same genera as those of the true Coal-measures, and half of 

 them, at least, have the same specific characters. Thus, it is evident that 

 the true Coal-measures descend as low as the Subcarboniferous Limestone 

 and even can be counted to the second bed of the Archimedes Limestone. 

 Not much coal is formed there, it is true, but it is the beginning, the 

 infancy of the epoch, which, as at the time of its decrepitude and near its 

 end, has the strata of combustible matter scarcely formed and thin. 



It is impossible now to establish a close comparison between the strata of 

 the Old Red Sandstone of Pennsylvania and the Subcarboniferous Lime- 

 stone of the West, which, following the assertion of some geologists, occupy 

 its place. From some data formerly collected, the Red Sandstone of 

 Pennsylvania had very few species, if any, identical with those of the Coal- 

 measures. It is characterized especially by the species of true Noeggera- 

 thia which have never been found in connection with the coal, and which 

 I have found in abundance in the red shales immediately underlying the 

 conglomerate formations of Mauch Chunk and Pottsville, and lower still. 



It would be even more difficult to compare the distribution of the plants 

 of the Coal-measures and of the New Red Sandstone or Permian overlying 

 them. The Permian is scarcely known in America, and no plants have 

 been found in it. But in Europe, the proportion of the vegetable species 

 common to the Permian and the Coal-measures is no more than eight per 

 cent, while between the Subconglomerate coal and the Coal-measures above 

 the Conglomerate, the proportion of common species is from fifty to fifty- 

 five. Moreover, with the appearance of the Permian, a number of entirely 

 different typical forms, mostly Coniferse (Araucarites, Walchia, Pinites, 

 &c), appear at once; and these forms having no relation whatever to the 

 genera of plants of the coal-measures indicate a new epoch in the vege- 

 tation. Thus it is certain, that if we should separate, as some geolo- 

 gists have done, the Subconglomerate coal as a peculiar formation, we 

 would do it against the general laws of distribution of the species and 



