CONTEXTS. 



Page. 



Introduction 755 



Application of tiie term " Potts^dlle formation " 755 



Agency of fossil plants in the correlation of the terranes 756 



Purpose and scope of this paper 757 



General description of the Southern field 759 



Form and extent of the field 759 



General geologic structure 759 



Description of the Pottsx^ille formati(.)u in the type region 762 



Composition of the formation 763 



Conglomeratic nature of the Coal Measures 766 



The Lykens or Pottsville coals 766 



Nomenclature of the coals 768 



The type paleobotanic section of the Pottsville formation 769 



Fossil-plant collections . 769 



Species and their observed distribution within the formation and field 771 



Paleontologic divisions of the formation 773 



Floras of the Lower Lykens division 790 



Flora of the Zero and No. 6 coals 790 



Flora of Lykens coal No. 5 791 



Paleontologic features of the roof shales of coal Xo. 4 792 



Comparison of the lower jiortion of the type section with reference to 



the Lykens coal horizons i 793 



Flora of the Lower Intermediate division 794 



Brief existence of a transition flora. 794 



Flora of the Upj^er Lykens division _ 795 



Flora of Lykens coals Nos.-3 and 2 795 



Flora of Lykens coal No. 1 798 



Upper Lykens zones in the type section 798 



Flora of the Uj^per Intermediate division 800 



Plants of beds ]M and N in the type section 800 



Correlations 803 



Paleontologic relations of coals developed at isolated mines in the Southern 



Anthracite field 803 



Horizon of the lower Lykens Valley coal in the Western Middle Anthra- 

 cite field, between Frackville and Shamokin 810 



Zones of the Pottsville floras in other regions of the Ai)palacliian province 812 



Clark formation 814 



Quinnimont formation 815 



Sewell formation 816 



Lookout formation 817 



Fayette samlstone 818 



Campbell Ledge, Northern Anthracite field 819 



Relative horizons of the l)asal Iteds of the thin sections as comi)ared to the 



thick eastern sections 820 



751 



