531 



[Claypole. 



B, Note on the occurrence of Holoiitychius, about 500 feet below the recog- 



nized top of the Chemung Group, in Bradford County. 



The base of the Castkill group has been assumed on palseontological 

 grounds at the lowest stratum in which the remains of the great Ganoid 

 fish Holoptychius Americanus have been found. Lithologically and strati- 

 graphically this dividing horizon has been placed where the green fossil- 

 iferous shales of the Chemung are supplanted by red shales and sandstones, 

 mostly without fossils. Sometimes these two principles of division give 

 coincident, sometimes discordant, results. Often the fossil remains can- 

 not be found, and almost as often the line between red and green material 

 cannot be firmly drawn. 



In Bradford county, however, these difiiculties do not occur. The green 

 rocks give place almost suddenly to the red ones, and the line between 

 Chemung and Catskill is easily drawn on stratigraphical evidence. The 

 red Catskill i-ocks also in many places abound in remains of fish near if not 

 at their base, consequently the two lines of evidence converge to almost 

 coincident results. The occurrence therefore of a well marked and un- 

 mistakable scale of Holoptychius Americanus considerably below the divid- 

 ing plane is a fact worthy of some notice. 



The scale in question is on the surface of a slab of green sandstone and 

 was quarried out of the solid rock by Mr. Lilley, of Leroy, when getting 

 stone for the foundation of a barn. Although I am unable at present to 

 determine exactly the position of the sandstone, yet from the fact that it 

 lies at a very small distance above the Mansfield Red bed with iron ore, it 

 must be not far from four hundred feet below the base of the Catskill 

 group, as recognized in this county. 



In further proof of the occurrence of the above-named fossil in this 

 horizon, I may add that while engaged with Mr. Lilley, in examining the 

 evidence for the presence of the Catskill, north of Franklindale, Mr. 

 L. picked up a loose slab of green sandstone showing on its surface 

 three large scales of Holoptychius. The point where it was discovered is 

 very near the horizon of the specimen first mentioned, the bed rock is 

 very near the surface, little or no drift material is present, the slab is not 

 rounded, and the Catskill rocks are on the other side of the valley of 

 Towanda creek. 



All this evidence concentrated, leads me to believe that this second 

 specimen is of Chemung age and comes from the same horizon as the 

 first. 



C. On a Mass of Catskill Bocks supposed to exist on the North Bank of 



Towanda Creek, near Franklin. 



Reference to the geological map of Bradford county will show a patch 

 colored to represent the Catskill on the north bank of Towanda creek, in 

 Franklin township. It measures about four miles in length by one in its 



PROC. AMER, PHILOS. SOC, XX. 113. 30. * PRINTED FEBRUARY 23, 1883. 



