GIRTY, GEOLOGIC AGE OF THE BEDFORD SHALE 307 



supposed significance has for one reason or another quite disappeared 

 under impartial criticism. 



Consideration seems to be demanded at this point of a small list of 

 "Carboniferous" species cited by Mr. Butts from the "Bradfordian" of 

 the Olean quadrangle. These species are not known in the Bedford 

 shale, but the Bedford interval is probably represented in the Olean sec- 

 tion, though not distinctly recognizable there. At all events, if the 

 Knapp and Oswayo formations of the Olean section are Carboniferous, 

 it is clear that the Bedford shale must be Carboniferous, whatever its 

 fauna, since if it does not represent some horizon in those formations, it 

 must represent one above, rather than below them. It is therefore ger- 

 mane to this discussion to scrutinize the evidence for calling the Knapp 

 and Oswayo formations Carboniferous. I suspect that the authors of the 

 work in which these species are cited would have proceeded differently if 

 they had not assumed as a postulate the general equivalence of the Olean 

 rock section with that of northwestern Pennsylvania and northeastern 

 Ohio, so that the question which they considered was not, "Is the Car- 

 boniferous actually represented in the Olean section?" but, "Since the 

 Carboniferous is represented in the Olean section, where should the line 

 best be drawn between it and the Devonian?" 13 



The "Carboniferous" types cited by Mr. Butts make up a total of but 

 seven out of a list of 59 species. All the rest are Devonian forms, most of 

 which, and possibly all, have never been found in rocks of Carboniferous 

 age, so that were we to consider the question whether the faunas show a 

 predominating Devonian or Carboniferous facies, there could be but one 

 answer. It is only by adhering to the rule of "first appearance" that 

 these formations can with any justification be called Carboniferous. 



Let us, however, consider the Carboniferous character of the seven spe- 

 cies on which this age determination depends. In addition to two fishes 

 referred to the Carboniferous genera Ctenodus and Gyr acanthus, the list 

 includes five invertebrates. These are Oehlertella pleurites, Orthothetes 

 crenistria, Glossites (Sanguinolites) amygdalinus ?, Sphenotus ceolus ?, 

 Crenipecten winclielli. 



I have already expressed the opinion that but little reliance can be 

 placed upon the Schuchertellas in matters of correlation because of the 

 difficulties of drawing any satisfactory lines between species or supposed 

 species in the genus. The significance in the present instance is still 



13 This reference of the Knapp and Oswayo formations to the Carboniferous has re- 

 cently been reaffirmed by Hartnagel (New York State Museum, Handbook 19, p. 87 

 et seq., April 1912), without the discussion that would seem to he demanded by the 

 subsequently known fact that these formations occur below the Waverly group of Ohio 

 (at least if the Berea sandstone is taken as the base). 



