iQig] BASSLER—SPORANGIOPHORIC LEPIDOPHYTE Q7 



Technical discussion of the species 



There now follows a discussion of the species of this genus which 

 will be technical and very brief, given in the interest primarily of 

 stratigraphic correlation, for we believe that the members of a 

 group with structure as intricate and diverse as this will have high 

 stratigraphic value if treated with great systematic refinement. 

 Details of structure already given will not as a rule be repeated 

 here, and the discussion will be further condensed by a tabulation 

 of the considerable number of dimensions involved. 



The stratigraphy of the Pennsylvanian Period in western Mary- 

 land and adjacent parts of Pennsylvania and West Virginia has 

 recently been studied critically by Charles K. Swartz, assisted 

 by W. A. Price and the writer, among others, and a preliminary 

 report on the results of these studies is about to be published by 

 the Maryland Geological Survey,^ but reference to the "horizon 

 of the Davis seam," to the "top of the Pottsville formation," and 

 to the "top of the Allegheny formation" in subsequent remarks, 

 calls for a very brief statement of final conclusions reached with 

 regard to the limits of the Allegheny formation, inasmuch as the 

 standard section for this region has undergone important revision. 

 In the Georges Creek basin the Ames or Crinoidal marine fauna 

 occupies a position about 550 ft. below the base of the Pittsburgh 

 seam; the Brush Creek marine' fauna, a position 250 ft. below 

 the Ames; and the Davis or "Split-six" coal (the topmost unit of 

 the Allegheny formation) , 1 1 5-1 20 ft. below the Brush Creek. ^ The 

 thickness of the Conemaugh formation is thus a little over 900 ft., 

 that of the Allegheny (upon stratigraphic and floral evidence) 

 about 265 ft., and the Pottsville from the base of the Allegheny 

 to the great unconformity at the top of the Mauch Chunk red shales 

 between 200 and 250 ft. 



Cantheliophorus linearifolius (Lesquereux) . — -The essential 

 characters of this species are a very long slender blade perpendicular 

 to the cone axis, a very large oblong sporangiophore with granulose 



^ A fuller discussion will be presented in the "Monograph of the Carboniferous 

 of Maryland," which will be published at a later date by the State Survey. 



7 To the westward of the Georges Creek basin there is a gradual thinning of that 

 part of the Conemaugh section above the Brush Creek marine horizon. 



