156 D. WHITE — RELATIVE AGES OF KANAWHA-ALLEGHENY SERIES 



Here, too, occasional representatives of the Pecopteris arborescens group, 

 P. arborescens, P. hemitelioides, P. cyathea, or P. lesquereuxii are found. The 

 writer is not certain of the presence of the true P. arborescens at any 

 point below the Freeport group. 



The post-Pottsville floras of the Pennsylvania sections are also well 

 marked by their Neuropteroid elements. Neuropteris vermicularis, gener- 

 ally characteristic of the low r er group of the Allegheny series, is usually 

 accompanied b}' N. rarinervis, while such forms as X. fimbriata, N. clark- 

 soni, N. griffithii, or N. crenulata, usually at higher levels, are readily 

 recognized. The ubiquitous Neuropteris ovata and N. scheuchzeri also 

 become somewhat modified in the higher beds, the pinnules of the former 

 developing larger and less broadly attached, while those of the latter 

 are more Ungulate and larger. The Ungulate and the cuneate-lobed 

 types of Odontopteris, as well as the entire genus Linopteris (Dictyopteris), 

 typified in Dictyopteris obliqua, appear to be wholly unknown below the 

 Allegheny series in the Pennsylvanian section; so with the broad, 

 obtuse-pinnuled species of Callipteridium. 



The Calamarian stems and the trunks of Lepidodendron and Sigil- 

 laria are of very inferior stratigraphic value as compared to the ferns. 

 However, in contrast to the Pottsville flora, the Allegheny flora is char- 

 acterized by the presence of Aster ophyllites equisettformis, Annularia stel- 

 lata, and A. sphenophylloides. The leaves of the first and last named 

 species are generally rather small in the lower group, but rapidly 

 develop to the typical proportions. Sj)henophyllum majus and S. emargi- 

 natum are both characteristic of the post-Pottsville beds. The last 

 named species, which in this country seems to have been confused with 

 S. schlotheimii, is generally omnipresent above the Homewood sandstone 

 or the " Buck Mountain conglomerate,'' while, on the other hand, below 

 the latter we find the very narrow, slender, and very lax form described 

 by Professor Lesquereux, from the upper Pottsville, as S. saxifragasfolium. 

 Even among the Lepidophytes we find such distinctive and well known 

 types as Lepidodendron modulatum, the group of large Lepidostrobi, such 

 as Lepidostrobus spectabilis, Lepidophyllum oblong if olium, and L. ovatifo- 

 lium, and the Sigillaria camptotsenia to be peculiar to the Allegheny series 

 or higher beds. Of the great diversit}^ of gymnospermous fruits, the 

 l'arge Cordaicarpa, the large, broad Pachytesta, types of Rhabdocarpos, as 

 well as a number of small fruits, such as R. mamillatus and Carpolithes 

 ellipticus, are evidence of a terrane as high as or higher than the Alle- 

 gheny series. It must not be inferred from the above that the Allegheny 

 series is marked by the introduction of new types rather than by the ex- 

 tinction of Pottsville forms. The Pottsville is characterized by a mode- 

 rately rich flora, the greater part of whose fern elements and nearly all 



