Important collections have been made in a few localities, and these will now be considered:

At Pittston, in Luzerne County, on Susquehanna River, have been found teeth of the horse Equus complicatus (p. [184]), remains of mastodon (p. [68]), and of a musk-ox (p. [248]). The presence of the horse makes it evident that the deposit containing the fossils belongs to a stage older than the Wisconsin, although the locality is within the area of the Wisconsin.

We consider now the contents of a cave found near Stroudsburg, Monroe County. The Hartman (or Crystal Hill) Cave was discovered in 1880 and explored first by Mr. T. Dunkin Paret, of Stroudsburg. It was soon afterward examined by Dr. Joseph Leidy, of Philadelphia, and Dr. Thomas C. Porter, of Easton. Leidy published the first description of it in 1880 (Proc. Acad. Nat. Sci. Phila., pp. 346–348) and presented a list of the species of animals which had been secured by Mr. Paret. In 1889 (Ann. Rep. Geol. Surv. Pennsylvania, for 1887, pp. 1–18, plates I, II), a more detailed report was made by Leidy, including descriptions and illustrations of some of the vertebrates and of certain artifacts which had been discovered.

In 1894, Dr. H. C. Mercer made a re-exploration of the cave and gave a more extended description of it (Proc. Acad. Nat. Sci. Phila., pp. 96–104).

Combining the statements of Leidy and Mercer with data obtained from the Delaware Water Gap topographical sheet issued by the U. S. Geological Survey, one finds that the cave is situated on Crystal Hill, about 3.5 miles in a straight line southwest of Stroudsburg and close to the village of Stormville. Crystal Hill is a part of an anticlinal fold, Godfrey Ridge, of the Helderberg limestone. South of the fold runs Cherry Creek; north of it, Mt. Michaels Creek. On the northeast the hill is cut off from the rest of the ridge by a valley about 300 feet deep. Mercer’s account states that the cave is on the top of the hill, about 0.25 mile from Cherry Creek, but the topographical map locates the top of the hill about 0.75 mile away from this stream. Mercer also wrote that the cave was 800 feet above Delaware River, 5 miles away. However, the hill has an elevation of somewhat less than 840 feet above sea-level, while the river at the nearest point is somewhat more than 280 feet above sea-level. Inasmuch as the cave is probably somewhere on the southern slope of the hill, it is about 500 feet above the Delaware and about 300 feet above the bed of Cherry Creek.

The opening of the cave in the rock was wide (Mercer, p. 96, fig. 1), but had become almost wholly choked by débris. Nevertheless, a hole large enough for adventurous boys to enter remained (Leidy, op. cit., 1880, p. 346). After a few feet descent the cave extended nearly horizontally more than 100 feet. It had become filled nearly to the roof by various deposits. Excavations showed that on top was a layer, about a foot, of “black friable earth mingled with animal and vegetal remains” (Leidy). Mercer describes it as a “top layer of limestone roof-splinters and down-slidden outer talus thinning inward into less stony cave earth.” Beneath this layer was a thin stratum of stalagmite. Further digging showed that below this stalagmite flooring the cave was filled to a thickness of as much as 14 feet in one place. This deposit is described by Mercer as being a continuous homogeneous bed of exquisitely fine clay deposited in thin laminæ rarely sprinkled with sand pockets and underlain with a thin film of sand. Neither in this deposit nor in the stalagmite was there found a trace of any formerly living thing. All the remains of animals and all the artifacts were discovered in the uppermost layer.

It should be noted at this point that this cave is situated about 5 or 6 miles north of the Wisconsin moraine.

The following is a list of the species of vertebrates identified by Leidy. When his names differ from those now in use they are inclosed in parenthesis.

List of species of vertebrates.