238 



flattened base from six to ten inches in width. The family of the Neu- 

 ropteridce is apparently the more g:enerally predominant in the Coal- 

 Measures. Some of its species are found in the Subcarbouiferous coal- 

 beds of Arkansas, where they are mixed with a large proportion of re- 

 mains of Lepidodendron ; they become most numerous in the Lower Coal- 

 strata above the Millstone Grit, together with large species of Aletho- 

 pteris, and sensibly diminish in passing up to the Upper Coal beds. Two 

 or three species only have been found with the Pittsburgh coal. In 

 Europe, one species, Neuropteris Loscliii, one of the most common plants 

 of the coal flora of both continents, passes up into the Permian. The 

 family of the Pecopteridw, some forms of which are comparable to species 

 of Pteris and of Cyathea of our time, has already some representatives 

 in the Lower Coal, especially species of Alethopteris, with large leaflets. 

 But it becomes more and more abundant in ascending, and in the upper 

 part of the formation it is the principal representative of the fern flora. 

 A beautiful species, Fecopteris arhorescens, has been found in barren 

 shales far above the Pittsburgh coal (or the productive Coal-Measures), 

 and in Europe at least it continues ou into the Permian. These Peeopte- 

 i^idce are generally represented by branches and leaflets, which, many 

 of them at least, are derived fragments from tree-ferns ; their trunks, 

 which are rare in connection with the Lower Coal beds, are locally very 

 abundant in the Middle and Upper Coal-Measures. 



In the family of the Lycopodiacece, the most interesting groups are 

 those of the Lepidodendroji, Ulodendron, Sigillaria, and Stigmaria, whose 

 characters, as taken from the scars of their bark, have been briefly re- 

 marked upon already. The remaius of Stifjmaria are especially numer- 

 ous in the whole thickness of the Carboniferous strata, and are dis- 

 tributed in every kind of rock except in the limestones. They generally 

 fill the clay-beds under the coal, often appearing as the essential com- 

 ponent of some of these beds, sometimes in a thickness of fifty feet or 

 even more. They represent the rhizomas, or floating stems, of the Lyco- 

 podiacea', — Lepidodendron, iSigillaria, etc., — these being the stems or trees 

 that bear cones as their fructification. We recognize the same confor- 

 mation in the club-mosses of our epoch, w^hich, like Lycopliodium inun- 

 datuni, L. arboreum, etc., have creeping stems bearing, ou the under 

 side, long, thread-like filaments penetrating the ground, or rootlets 

 creeping in wet mosses or soft mud, while their fruit-bearing stems 

 are erect and have leaves and cones. The more ancient lycopodiaceous 

 representatives in the coal are the Lepidodendron. The Siglllaria appear 

 later and persist longer. While Lepidodendron species have not been 

 as yet recognized in connection with the Pittsburgh coal, many species 

 of iSigillaria are there. Sigillaria Brardei has been found, filliug by its 

 remains a bed of sandy shale far above the Brownsville coal, which is 

 the highest workable bed of Pennsylvania, already three hundred feet 

 above the Pittsburgh coal. In Europe, one species at least of this last 

 genus passes up to the Lower Permian. 



The Equisetacece, or Horsetail species of the present time, have 

 cylindrical, articulated stems, scarcely measuring one inch in diameter. 

 The principal species of this group occurring in the Coal -Measures, the 

 Calamites, were trees similar in their structure, with hollow articulated 

 trunks and striated surfaces, but comparatively of great size; their trunks 

 varying from two to eight inches in diameter. Their branches were 

 borne at and around the articulations, and they had at the nodi whorls 

 of narrow, small, linear-lanceolate, sharply-poiuted leaves. As these 

 branches aie rarely found attached to their stems, they were for a long 

 time considered as representing distinct species, and separated in the de^ 



