418 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [May 20, 



whether I confirmed or invalidated his conclusions. I shall first 

 speak of the reptilian foot-marks. 



The quarry where they were found is about five miles S.E. of 

 Greensburg, in the county of Westmoreland, Pennsylvania. The stone 

 quarried is a sandstone which rises up from beneath the main or Pitts- 

 burg seam of coal, which has been worked at its outcrop in the im- 

 mediate neighbourhood*. There are several other seams of coal, 

 which lie at lower levels, and impressions of Lepidodendron, Sigil- 

 laria, Stigmaria, Calamites, Ferns, and other plants have been found 

 in the beds which lie above and below the sandstone containing the 

 foot-marks. The slabs of sandstone, which are extracted in the 

 quarry for paving, are separated by parting layers of a fine unctuous 

 clay, such as would be admirably fitted to receive the most delicate 

 and faithful impressions of the feet of animals treading upon it. 



One of these Cheirotherian impressions was observed by Dr. King 

 imprinted on the upper surface of one of the layers of clay or shale 

 before-mentioned, but the specimen was unfortunately left exposed, 

 and was destroyed by the weather. Twenty-two other footsteps 

 were discovered on the under sides of the slabs of sandstone, stand- 

 ing out in relief from a surface which also exhibits those large and 

 small mud-veins, which are the casts of cracks produced by the dry- 

 ing and shrinking of the mud on which the animal walked. The 

 shrinkage took place after the foot-marks were made, so that these 

 prints were traversed and slightly distorted by the cracks. The 

 casts of these shrinkage cracks were mistaken for Fucoids. 



The Cheirotherian tracks occur in pairs, each pair consisting of a 

 hind- and fore-foot. There are two rows of these, which are parallel, 

 or have been formed, the one by the right fore- and hind-feet, the 

 other by the left; the toes turning one set to the right and the 

 others to the left, and the distances between the successive footsteps 

 being about the same throughout. 



I shall now advert to the supposed foot-prints of birds, and of 

 quadrupeds resembling dogs, cloven-footed and other animals. 



The principal place where these imprints were observed, and which 

 I visited, is about a mile distant from the town of Derry in West- 

 moreland county, Pennsylvania. They were not found beneath the 

 soil, nor on the under surface of solid strata, like the Chirotherian 

 marks at Greensburg, but consisted of impressions or incisions on 

 the upper surface of a denuded ledge of white coal-grit or sandstone, 

 which has been exposed for ages, and so acted upon by water, that 

 channels and cavities have been shaped out, and numerous deep 

 pot-holes, some of them more than a foot in diameter and eighteen 

 inches deep, excavated in it. To suppose a series of deep and sharp 

 foot-prints of birds to have been retained unblunted by weathering, 

 or by the currents of water which denuded the sandstone, would be 

 sufficiently difficult ; but still more to account for the fact, that the 

 last of the imprints is on the steep end of the ledge, inclined at an 



* " The Pittsburg seam is 10 feet thick, and has been ascertained to occupy an 

 area of about 14,000 square miles." — LyelVs Travels in America, vol. ii. p. 27. 



