Raymond: Sections in the Conemaugh Series. 177 



is a discontinuous layer of limestone nodules which Professor Steven- 

 son states (Bulletin Geological Society of America, Vol. XVII, p. 174, 

 1906) represents the Brush Creek limestone. That this is a correct 

 correlation is confirmed by the discovery by the writer of specimens 

 Eiiomphalus ca/i//oides, Pleurotonuvia carbonaria, and a Nautilus in 

 the shale less than a foot above the limestone. The fossils were not 

 common and were poorly preserved, but enough could be deter- 

 mined to show that it was a marine fauna, similar to the fauna found 

 elsewhere in the shale above the Brush Creek. The sandstone at 

 Saltsburg thus overlies the Brush Creek as does the Buffalo, but the 

 Pine Creek is absent from the section at Saltsburg, its place being oc- 

 cupied by sandstone. The Cow Run and the Buffalo have apparently 

 joined, as at Allegheny. The name Saltsburg was applied to the whole 

 mass, and thus has a different meaning from the name Buffalo, which 

 can be applied to only the lower part of the sandstone at Saltsburg. 



EXPLANATION OF PLATES. 



Plate XI L 



A diagrammatic section of the strata exposed in the bluff along the Ft. Wayne R. 

 R. from Jack's Run to Wood's Run, Allegheny, Pa. The lower diagram is a con- 

 tinuation of the upper. Vertical scale, i inch equals 120 feet; horizontal scale, I 

 inch equals 600 feet. 



Plate XIII. 



Upper photograph. The bluff just south of the small ravine indicated in the dia- 

 gram on the preceding plate. The Pine Creek limestone (just at the top of the poles 

 in the picture) and the clay beneath it are seen to be cut out near the margin of the 

 photograph. The soft bed beneath the limestone is the green clay of the diagram, 

 beneath it is the Buffalo sandstone, extending a little below the fence, and in the shale 

 beneath the sandstone is the Brush Creek limestone. 



Lower photograph. A nearer view of the face of the bluff just at the left-hand 



margin of the upper picture, showing the shale resting on the eroded edges of the 



Buffalo sandstone. 



Plate XIV. 



Upper photograph. Unconformity at the base of the Buffalo sandstone one mile 

 north of Etna, Pa. The hammer rests on the Brush Creek limestone. Above it is 

 a cross-bedded shale, followed by the Buffalo sandstone. 



Lower photograph. Unconformity at the base of the Buffalo sandstone along 

 the Pennsylvania Railroad near Wood's Run, Allegheny, Pa. 



