WHITE.] FLORAL ZONES OF THE FOTTSVILLE FORMATION. 803 



CORREI^ATIOIS^S. 



It is not within the scope of this paper, whose primary purpose is to 

 present a combined stratigraphic and paleontologic type section and 

 definition of the Pottsyille flora in the type region, to enter in detail 

 into the subject of the correlation of the yarious terranes and groups 

 in the Appalachian trough which haye been or should he regarded as 

 equiyalent to the whole or a part of the Pottsyille formation as deyel- 

 oped in the Southern Anthracite field. Such a treatment of these 

 extensiye and complicated problems can be satisfactorih' accomplished 

 only in connection with the consideration of the detailed paleonto- 

 logic evidence of all the terranes concerned in the comparisons. 



In this report questions of contemporaneity will be confined to beds 

 at isolated localities in the anthracite region, or to formations or 

 groups in other regions whose floras are already more or less known, 

 and which will be correlated onl}" in a broad sense. 



These cases will be divided into two groups: (1) Detached localities 

 which are situated within the Southern Anthracite field itself and 

 whose actual occurrence in the Pottsyille formation in the typical 

 region renders this correlation more important as well as certain, 

 while at the same time adding to our knowledge of the distribution 

 and range of the species in the Pottsyille Basin. (2) Terranes or 

 groups whose floras have been studied in other fields. 



In discussing the beds of the first category greater confidence will 

 be reposed in the occurrence, in a given bed, of the particular group- 

 ing or association of species which, in the beds or sections alread}^ 

 discussed, appear to be characteristic of the several horizons, although 

 the number of species from the locality in question may be small. On 

 the other hand, in considering the relative age of formations geograph- 

 ically more remote, greater stress will be laid on the composition of the 

 entire flora, and on the vertical range of its elements as well as the pro- 

 portion of its identical species. 



PALEONTOLOGIC RELATIONS OF COALS DEVELOPED AT ISO- 

 LATED MINES IN THE SOUTHERN ANTHRACITE FIELD. 



The principal detached localities, within the limits of the Southern 

 Anthracite field, from which fossil plants have been obtained are those 

 inscribed to the right of the columns devoted to the type section in 

 the table of distribution. All of these have at some time been the 

 scenes of coal exploitatioii or prospecting. In most cases the beds have 

 been either tentatively or definitely, and, as Avill ])e further shown, some- 

 times erroneously, correlated with reference to the Lykens coals mined 

 in the Lincoln-LyktMis region. Several of these localities are but a few 

 miles from the mining developments of the latter region, and nearly all 

 are east of the mines. The correlation of these beds, so far as it can 



