172 Annals of the Carnegie Museum. 



5. Yellow structureless^lay. 5 ft 217 ft. 6 in. 



4. Gray and yellow shale, grading into thin-bedded sandstone. 36 



ft. 6 in 254 ft. 



3. Gray clay-shale overlying i ft. 7 in. of sandy limestone, both 



containing numerous marine fossils. Brush Creek horizon. 4 ft. 258 ft. 



2. Yellow, almost structureless clay. 9 ft. 6 in 267 ft. 6 in. 



I. Heavy-bedded sanistone, base not seen. 10 ft. 6 in 278 ft. 



This section does not differ greatly from the one given by Professor 

 Stevenson in Report KK, page 348, figure 48, which was measured 

 along the old line of the Pennsylvania Railroad. His No. 15 corre- 

 sponds to our No. 20 and is not the Morgantown but a sandy phase of 

 the Birmingham. Dr. Stevenson's " coaly shale " No. 27, is the Pipe 

 Creek and No. 30 is the Brush Creek. The Pine Creek here contains 

 very little lime and in the cuts east of the one at Trafford can hardly 

 be distinguished except by its few marine fossils. In the cut just east 

 of Trafford it forms a fairly solid layer, sometimes a foot thick, and 

 contains quite a quantity of fossils, chiefly cephalopods and gastropods. 



The strata between the Pine Creek and Ames limestones here 

 measure 112 feet as compared with no feet at Donohoe. As shown 

 by the sections the intervening beds are quite different at the two 

 localities. The Cow Run sandstone is absent from this section, as is 

 the Harlem coal. The coal may, however, be seen on the western 

 side of this anticline along the road between Wilmerding and Pitcairn. 

 Bed 13 of this section is the same as bed 28 of the section west of 

 Beatty, and 10 is at the same horizon as 24. 



The vertical distance between the Brush Creek and Pine Creek lime- 

 stones is only 52 feet, in place of 90 feet at Donohoe, and what sand- 

 stone there is between the two limestones is not massive, but rather 

 thin-bedded and shaly. 



Note on the Unconformities at the Lower Limits of the 

 Buffalo and Cow Run Sandstones. 



The unconformities at the bases of the Cow Run and Buffalo sand- 

 stones are well shown along the bluff above the Fort Wayne Railroad 

 tracks between Allegheny and Bellevue, Pa. This locality is men- 

 tioned by Dr. L C. White, in Report Q, page 165, of the Second 

 Pennsylvania Survey, but was not described in detail. It is such a 

 good example of the unconformities by erosion which occur at these 

 horizons that the section is here illustrated by means of a diagram and 

 photographs. The diagram (Plate XII) is drawn to scale, the vertical 



