As already said, there are admitted into the list given above, as identified in a reasonably good manner, 60 species, of which 54 belong to the Mammalia. It is a matter of interest to compare these with the species of mammals which were living in that general region before the fauna was disturbed by the arrival of the whites. The number of species of the existing mammals, as shown in the second column, is obtained from Rhoads’s “Mammals of Pennsylvania and New Jersey.” The subspecies are not included.
| Families of land mammals represented in Port Kennedy Cave and those that have lived in that region within Recent times, together with the number of known species in each family at each of the two epochs. | ||
|---|---|---|
| Families. | No. of species, Port Kennedy. | No. of recent species. |
| Megatheriidæ | 5 | |
| Didelphidæ | 1 | |
| Equidæ | 2 | |
| Tapiridæ | 1 | |
| Tagassuidæ | 3 | |
| Camelidæ? | 1 | |
| Cervidæ | 2 | 2 |
| Bovidæ | 1 | 1 |
| Elephantidæ | 1 | |
| Sciuridæ | 1 | 6 |
| Castoridæ | 1 | 1 |
| Cricetidæ | 7 | 9 |
| Zapodidæ | 1 | 2 |
| Erethizontidæ | 1 | 1 |
| Ochotonidæ | 1 | |
| Leporidæ | 1 | 2 |
| Soricidæ | 1 | 5 |
| Talpidæ | 1 | 3 |
| Vespertilionidæ | 1 | 8 |
| Procyonidæ | ? | 1 |
| Ursidæ | 2 | 1 |
| Mustelidæ | 11 | 9 |
| Canidæ | 4 | 3 |
| Felidæ | 5 | 3 |
In the column of fossils there are 54 species; in that of the Recent there are 58 species. Of two families represented at present in the region, but not included in the Pleistocene column, Didelphidæ and Procyonidæ, the latter named has had remains referred to it with doubt. Without doubt members of both families existed there at that time.
Of the families of the Pleistocene column two no longer live anywhere near the region; four nowhere on the continent; one nowhere on the earth. Even of such families as the Ursidæ and the Felidæ important elements, as Arctotherium and the saber-tooths, are extinct. Of the 54 species admitted in the Pleistocene column 40 are extinct; that is, 74 per cent.
If we consider the sizes of the animals in question we gain this result: Only 15 of the existing species are of any considerable size, ranging from that of a raccoon to that of a bison, about 26 per cent. Of the 54 fossil species of mammals, about 30 vary in size as indicated, about 57 per cent. It is hardly to be doubted that this preponderance is due to the poorer chances which the smaller skeletons had of preservation and of rescue from the matrix. Had the smaller fossil species been preserved and collected in the same proportion that the smaller existing ones have to the larger, the cave ought to have furnished twice as many species of mammals as it did. It is, of course, possible that the larger species are more liable than the smaller ones to become extinct as time passes on. We can hardly doubt, in any case, that when the Port Kennedy animals were being buried in that cave there lived in that region a considerably larger number of species than within Recent times. There must have existed in that region more moles, more rabbits, more cricetids, more squirrels, and many more bats. Certainly there is no adequate record of the number of birds, snakes, turtles, and amphibians that must have existed about Port Kennedy and have perished in that cave.
From the collection that has been made in the cave at Port Kennedy some definite conclusions ought to be reached regarding their time of existence. In his account of the cave and of the exhumation of the animal and vegetable remains, Mercer (1899, pp. 269–286) has shown what extreme care was taken in recording the position which each specimen occupied in the deposits. In his figure 9 he has noted the levels which the various species occupied. While the existence of four beds of materials makes it evident that the deposition went on for some time, it is noted that few or no differences exist in the character of the species included. Possibly Mercer’s subdivision 1 is to be excepted in this statement. Certainly no great changes went on in the fauna while the cave was being filled; no such changes as occurred in the glaciated region from the Aftonian interglacial stage up to the Late Wisconsin. It appears more probable that the deposits in the cave and the animals entombed there appertain to about a single Pleistocene stage. Is, then, the stage the Late Wisconsin?
This cave is situated only about 55 miles south of the Wisconsin moraine. At the time the species found in the cave existed they must each have occupied a wide extent of territory. It is not to be doubted that the range of nearly every species extended northward far beyond the moraine mentioned. Why, then, in deposits overlying the Wisconsin drift have there never been found any remains of the four Port Kennedy species of Megalonyx, of Mylodon, of the two species of horses, of the tapir, of the three species of peccaries, of the deer Odocoileus lævicornis, of the five extinct species of cricetids, of Ochotona, of the extinct species of Blarina, of the great bear Arctotherium, of the six extinct species of skunks, of the extinct otter, of the extinct dog, of the extinct fox, of any species of saber-tooth tiger, or of the extinct cats Felis inexpectata and Lynx calcaratus? The absence of so many species of animals, most of them of large size, from deposits so well adapted to preserve bones and teeth, render it very certain that the animals no longer existed there.
Did the extinct species which are referred to above exist in eastern Pennsylvania at some time during the Wisconsin glacial stage and perish before the close?
A few of the species found in the cave and still existing are at present inhabitants of regions somewhat more northerly than Port Kennedy. Such are Erethizon dorsatum and Gulo luscus; but the great majority, living and extinct, indicate a climate at least as warm as that of the present; many of them suggesting a still milder condition. Within historical times both of the species just named have inhabited the Alleghany Mountains at least as far south as Port Kennedy. Cope, in 1871 (Proc. Amer. Philos. Soc., vol. XII, p. 99), concluded that he had then identified in the cave remains of 11 neotropical species. It appears, therefore, wholly improbable that this assemblage of animals lived in that region, so close to the foot of the glacier, during the Wisconsin stage. These animals must have had their time of existence previous to this inhospitable epoch. It seems to the writer that the proportion of extinct species, three-fourths, and the history of many of the genera and species, indicate a time about equivalent to the Aftonian.
Professor A. Heilprin (Proc. Phila. Acad. Nat. Sci., 1895, p. 451) expressed himself as being inclined to refer this cave fauna to the Pliocene. An examination of this opinion would show that it is no more tenable than the opinion that the fauna is of the Wisconsin stage. It will not be discussed here beyond saying that deposits containing a similar fauna are found along the Atlantic coast from New Jersey to the Gulf, and that at one place at least, Vero, Florida, these are underlain by abundant Pleistocene sea-shells.