Besides the vertebrates which have been listed, a number of beetles were found and about 10 specifically determined plants. Wheatley (1871, p. 385) presents a list of the beetles as determined by Dr. G. H. Horn, but the names were not accompanied by descriptions. When later (Trans. Amer. Entom. Soc., vol. V, 1876, pp. 241–245) Horn came to describe them he reduced the number of species and, in some cases, gave them other names. The following is a list as given in Horn’s paper just cited: Cychrus wheatleyi, C. (minor), Pterostichus (spp. indet.) Cymindis aurora, Chlænius punctulatus, Dicælus alutaceus, Choeridium? ebeninum, Phanæus antiquus, Aphodeus precursor. All of these, as the writer is informed by Dr. E. A. Schwarz, of the U. S. Department of Agriculture, are regarded as extinct, but as closely allied to species now living in that general region. The plants, as reported by Mercer, are Quercus palustris, Q. alba, Q. macrocarpa, Fagus ferruginea, Corylus americana, Pinus rigida, Carya porcina, C. alba, Ampelopsis quinquefolia, Cratægus crus-galli?, and all still flourish in eastern Pennsylvania.
Fig. 11.—Section of Port Kennedy bone cave at time of first exploration, 1871. Redrawn from Mercer.
M, M, Triassic shale; AL, Triassic shale; B, black clay, with leaves, etc.
Mercer (1899, p. 269) has given a description of the cave found in quarrying operations. It was located on the right bank of the Schuylkill River, at the village of Port Kennedy and about 2 miles below Valley Forge. Wheatley (1871, p. 236) gave a map which showed the position of the quarries. A comparison of this with the topographical map of Folio 162 of the U. S. Geological Survey shows that they were situated about 800 feet away from the river and facing the valley of an unnamed streamlet. None of the descriptions give the elevation of the cave above the river or above the sea. The river at that place is apparently about 70 feet above sea-level. The 100–foot contour-line runs along near the location of the quarries, but these may have extended back to a higher level. Putting all of the statements together, it appears probable that the mouth of the cave was, in Wheatley’s time, about 50 feet above the level of the river. Originally the surface elevation may have been still greater, but may have been reduced by erosion of the hill. The surface rock here is red shale of the Stockton formation, belonging to the Triassic, and is underlain by the Shenandoah limestone, a member of the Cambro-Ordovician series. This limestone was being quarried in 1871, when a cave was broken into, filled with incoherent materials and exposing fossil bones in abundance. It was visited by Charles Wheatley, who proceeded to make excavations and collect the fossils. In studying the fossils he worked with Professor E. D. Cope and Dr. G. H. Horn. The results were published in Wheatley’s two papers of 1871 and in two papers by Cope in the same year (Proc. Amer. Philos. Soc., vol. XII, pp. 15, 73–102). According to Wheatley’s description and his figures, the part of the cave seen was about 20 feet wide at the top, expanded below to about 30 feet, and then narrowed at the bottom, as then recognized, to about 10 feet. The depth was given as 40 feet, but Mercer thinks that this was improbable and that Wheatley’s measurements were to some extent guesses. Mercer (1899, p. 271) stated that this cave might be compared to a bottle of unknown size. It had opened to the surface; and on his page 283 Mercer spoke of it as forming a well-like hole that might have been as much as 70 feet deep. Evidently Mercer here included that part of it which he himself excavated. The materials filling it were, according to Cope (1871, p. 73), the débris of the neighboring Triassic strata. Figure 11 is taken from Mercer’s paper and is a reproduction of a sketch made by Wheatley in 1871. After Wheatley had made his collection the cave was covered over by débris from the quarry and forgotten.
Fig. 12.—Section of Port Kennedy bone cave at time of last exploration, 1894. Redrawn from Mercer.
In the course of further quarrying operations the same cave was broken into again in 1893. Excavations in the materials that filled the cave were made in 1894 by Dr. Samuel Dixon, H. C. Mercer, and others, resulting in the securing of the collection which formed the subject of Cope’s paper of 1894 and his final report of 1899. At this time, according to Mercer, the quarrying operations carried on from 1855 had transformed a gently sloping hillside into an amphitheater several acres in extent, walled with perpendicular escarpments of rock, sometimes a hundred feet high. At this time the floor of the quarry had been lowered and the cave was broken into at a level below that reached by Wheatley. Figure [12], reproduced from Mercer’s figure 5, shows the relation of the later excavations to those of 1871. As already stated, Mercer concluded that Wheatley’s dimensions were probably results of guesses, inasmuch as the top of Mercer’s exposure was not more than 30 or 33 feet below the original level of the hilltop. According to Mercer’s figure 5, his own excavation probably extended down about 16 feet below the level reached by Wheatley; but other statements appear to make this somewhat greater.
Mercer wrote that the materials filling the cave had been stratified by the action of water. He recognized four subdivisions, most of which stood higher around the walls than at the center of the cave. Of these subdivisions, the first and uppermost was supposed to mark the lowest level attained by Wheatley. It consisted of fine clay and loam of black color, intermingled with fine and coarse muck, in which were found some remains of small mammals, just what species was not stated. On his chart, his figure 9, a tapir is indicated as occurring in it. Subdivision 2 was composed of from 4 to 11 feet of sandy clay, with fragments of sandstone and limestone, from small ones up to about 2 feet in diameter. In this matrix there were numerous bones and teeth of large animals, but it lacked small ones and vegetal matter. Subdivision 3 was a sandy clay, blackened by vegetable matter and containing numerous bones of vertebrates, large and small. The lowest subdivision, 4, was a zone which was followed down about 10 feet and which consisted of sand, clay, and stones, all of a yellow color. In this were found remains of the larger mammals, better preserved than in the upper subdivisions. At the lowest depth reached the excavation appears to have extended below the level of the Schuylkill River and the water came in so rapidly that further descent was not practicable.
Mercer’s theory of the filling of the cave is expressed in these words, on his page 277:
“Enough had been seen to convince us that a fresh-water flood, rising to a level of from 15 to 20 feet above the present level of the hilltop, hence a general inundation of the whole surrounding country, bearing in its current the clay, stones, and earth of neighboring levels, had tumbled into the fissure, carrying with it the bones of creatures previously denuded of flesh and softened by decomposition.”