FOSSIL PLANTS. 503 



large tree in the Devonian of Ohio; in the Upper Silurian and Lower Devo- 

 nian of Pennsylvania, (1) and occur in abundance in the Chester group (Lower 

 Carboniferous) of Illinois. Representatives of this family of plants become 

 more and more predominant in ascending, and by the number of species, and 

 the size of the trees, the group attains its full development near the base 

 of the true Coal Measures, at the horizon of coal No. 2. The bed of shale 

 overlaying the Sub-Conglomerate coal of Kentucky and Arkansas, appears gen- 

 erally as a compound of mere debris, especially the leaves of Lepidodendra. 

 This coal, like that of No. 2, shows also, upon its horizontal layers, distinct 

 remains of plants of the same kind. In Pennsylvania, the shale of the mam- 

 moth bed, which I consider as the equivalent of coal 2, is, in places, a com- 

 pound of large pieces of the bark of Sigillaria and Lepidodendra, superposed 

 in a thickness of one to two feet, like the leaves of a book. (2) At Cuyahoga 

 Falls, Ohio, the shale of the same coal is, in places, a mere compound also of 

 pieces of bark of Sigillaria, and in Illinois, as seen by our table, the remains 

 of Sigillaria and Lepidodendra predominate in the shale of coal No. 2, and 

 the place of this coal in the sandstone of Marseilles is marked by remains 

 of large trees of the same genera. 



Ascending higher in the Measures, the Lycopodiaceous plants decrease in 

 number to coal No. 5, or to the Duquoin coal, which, from its vegetable re- 

 mains, appears to be the equivalent of coal No. 3. of the Kentucky Reports. 

 This family is here represented still by some species of Lepidodendron, Lepido- 

 phloios, by cones or Lepidostrobi of large size, and by a few Sigillaria of the 

 Lepidodendroid type, viz. : Sigillaria sculpta and 8. Brardei, which appear to be 

 universal species of the Carboniferous epoch. In higher strata of the Coal 

 Measures of the United States, species of Lepidodendra have not as yet been 

 found. 



In connection with the Pittsburgh coal, as with coal No. 9 and No' 11, of 

 Kentucky, I have seen specimens of the two last named species of Sigillaria, 

 but no remains of Lepidodendra. From horizons above the Pittsburgh coal, 

 we know nothing as yet of the flora of our Coal Measures. But in Europe, 

 G-oppert, in his flora of the Permian, enumerates Sigillaria Brardei, and de- 

 scribes two new species, 8. denudata and 8. Danziana, which are nearly related 

 to Sigillaria sculpta, Lesqx., if not identical with it. The same work men- 

 tions also, as found in the lowest strata of the Permian Measures, Lepidoden- 

 dron Veltheimianum, already present in the Devonian of Europe, and with us 

 in the Lower Carboniferous limestones of Illinois, and with it he describes a 



(1) Perm. Geol. Rep., p. 829, fig. 675, 677. 



(2) A shale of this kind is, by an abrupt flexure of the coal strata, thrown up near Trevor- 

 ton, and exposed as a perpendicular wall. 



