WHITE.] POTTSVILLE FLORAS IN OTHER REGIONS. 813 



paleontologie features of the different coal horizons of the Pottsville 

 formation, as outlined in an earlier part of this report (p. 773), it will 

 be recalled that on the basis of the vertical distribution of the contained 

 floras, so far as they have been brought to light, the formation was 

 divided primarily into (1) a Lower Lykens division, including the roof 

 shales of No. 4 in the mining region and bed D of the type section, and 

 extending downward to the red shale; and (2) an Upper Lykens divi- 

 sion, including Lykens coals Nos. 3 and 2 and the roof of Lykens coal 

 No. 1, or beds H to L, inclusive, in the type section. In beds E and F 

 (PI. CLXXXI) of the type section, comprising what 1 have designated 

 the Lower Litermediate division, there appears to be some inter- 

 mingling of the Lower and Upper Lykens species, while in beds about 

 225 feet below the conventional base of the Lower Coal ^Measures, or 

 perhaps nearly 100 feet below the paleontologie base, we find another 

 flora of somewhat mixed composition, suggesting the term "Upper 

 Intermediate division.'' The two intermediate divisions are thin as 

 compared with the whole formation. 



Of the two zones in the Lower Lykens division, the lower, including 

 the horizon of Lykens coal No. 5, is characterized by a relatively 

 simple flora. This, as indicated in the discussion of the floras of the 

 several coals, consists principal!}' of Xeuropteris. Pocahontas^ which is 

 always present and overwhelmingly abundant, its variety j?«?/?i/t/.y being 

 peculiar to this zone. It is also marked b}- the absence of the forms 

 characteristic of and conflned to the upper zone of the division, as the 

 latter is represented in the roof shale of coal No. 1. The plants 

 below coal No. 5, in the basal portion of the formation, are not suffi- 

 ciently known for the discovery of any special zonal types. No 

 attempt will therefore be made to determine in other regions any 

 equivalents of this basal portion of the section, although certain 

 inferences are unavoidable. 



The continued study of the Paleozoic floras along the eastern margin 

 of the Appalachian trough fully confirms the conclusion I stated some 

 years ago,' that it is only in the lower portions of the very thick sec- 

 tions of the Pottsville formation in this province that the oldest floras 

 are to be found, and that in general the very thin sections (e. g., along 

 the northern and northwestern margins of the trough) correspond only 

 to the upper portions of the sections of great thickness on the eastern 

 and southeastern shores of the basin. The correlations suggested 

 below will incidentally serve to illustrate this fact. However, since in 

 this report, which is })ut preliminary to a monograph of the Pottsville 

 flora of the Appalachian province, the correlative significance of the 

 floras will be treated in ])riefest possi])le form, without enumeration of 

 the characteristic species or the full presentation of the paleontologie, 



'Bull. Geol. Soc. America, Vol. VI, 1895, pp. 319-320. 



