606 PKOCEEDINGS OF THE ACADEMY OF [DeC. , 



quarry, in 1889, all the above-mentioned kinds of impressions were 

 found, except the Dinosaur tracks; and, in addition, impressions 

 of a plant were collected that may be a Baiera. 



The excursion party of October 26 also, on tlie way home, visited 

 a quarry on the roadside, on the southeast side of Skippack creek, 

 about three-eighths of a mile southwest of the main road between 

 CoUegeville and Norristown, near a mill across the creek. The 

 (|uarry is in dark red, hard, shaly sandrock of what is marked on 

 the State Geological map of the two counties as Gwynedd shales, 

 some 900 feet geologically below their top. The dip here is about 

 12° northwesterly. Here a large fossil Cycad leaf was found, 

 about twenty-one inches long by eight inches wide. It is expected 

 that this block will also be brought to the Academy. It may be, 

 as Miss ^Valter suggests, Pterophyllum spatulatiim. 



The party thence proceeded southward to Eagleville, on the top 

 of a hill of the Gwynedd shales. These comparatively hard dark 

 shales all along their outcrop make j^rominent hills, with the lower 

 lands formed on the southeast of them by the softer and in greater 

 part red, but further south gray, Norristown shales, and on the 

 northwest by the likewise softer and almost universally bright red 

 Lansdale shales, succeeded northward by the harder and in great 

 part greenish or blackish Perkasie shales, again with higher hills, 

 and yet further north by the softer red Potlslown shales. This 

 succession of beds of distinct character, with their outcrop of 

 special topographical character extending throughout the two coun- 

 ties, all conforming uniformly to several variations of structure, 

 with corresponding curves in the strike of the beds and everywhere 

 with correspondence in the dips, and with no evidence whatever of 

 any repetitions of the same sets of beds (except near the great 

 Buckingham ISIountain fault), is convincing proof that there is no 

 overthrust fault parallel to the strike that could diminish the 

 apparent total thickness of the beds. Such a fault, indeed, would 

 have to be of wonderful shape, in conformity to a somewhat com- 

 plicated folding of the beds. It is, moreover, in the highest degree 

 improbable that such faults, the result of excessive horizontal pres- 

 sure, with beds of great stiffness and cohesion, necessarily causing 

 extremely steep and overturned dips, could occur in a region of 

 gentle dips and mainly soft beds. 



The foot tracks, ripple marks, raindrop impressions and sun 

 cracks found at Fisher's (piarry, the Cycad leaves and the raindrop 

 impressions at the Skippack quarry, and other impressions and sun 

 cracks at many other points in the New Red of this region, show 

 clearly that the rocks were laid down in an estuary that was 

 shallow through a great part of the process, if not throughout. 

 There must have been submergence to correspond with the accumu- 

 lating beds, and doubtless caused oy their weight upon this portion 

 of the earth's crust. As the sedimentary material has plainly 



