Its hanging lower jaw, with the protruding tusk, corresponds perfectly to the formation of the lower jaw and teeth in the Manatee. Some resemblance of the Dinotherium to the Mastodon suggested a comparison with that animal as the next step in the investigation, when it was found that at the edge of the lower jaw of the latter there was a pit with a small projecting tooth, also corresponding exactly in its position to the tusk in the Dinotherium. The Elephant was now examined; and in him also a rudimentary tooth appeared in the lower jaw, not cut through, but placed in the same relation to the jaw and the other teeth as that of the Mastodon. It would seem, then, that the Manatee makes one in this series of Dinotherium, Mastodon, and Elephant, and represents the aquatic Pachyderms, occupying the same relation to the terrestrial Pachyderms as the Seals bear to the terrestrial Carnivora, and, like them, lowest in structure among their kind.
The announcement of Cuvier's results stimulated research, and from this time forward Tertiary Mammalia became the subject of extensive and most important investigations among naturalists. The attention of collectors once drawn to these remains, they were found in such numbers that the wonder was how they had been so long hidden from the observation of men. They remind us chiefly of tropical animals; indeed, Tigers, Hyenas, Rhinoceroses, Hippopotamuses, Mastodons, and Elephants had their home in countries which now belong to the Cold Temperate Zone, showing that the climate in these latitudes was much milder then than it is at present. Bones of many of these animals were found in caverns in Germany, France, Italy, and England. Perhaps the story of Kirkdale Cave, where the first important discovery of this kind was made on English soil, may not be so well known to American readers as to forbid its repetition here.
It was in the summer of 1821 that some workmen, employed in quarrying stone upon the slope of a limestone hill at Kirkdale, in Yorkshire, came accidentally upon the mouth of a cavern. Overgrown with grass and bushes, the mouth of this cave in the hill-side had been effectually closed against all intruders, and it was not strange that its existence had never been suspected. The hole was small, but large enough to admit a man on his hands and knees; and the workmen, creeping in through the opening, found that it led into a cavern, broad in some parts, but low throughout. There were only a few spots where a man could stand upright; but it was quite extensive, with branches opening out from it, some of which have not yet been explored. The whole floor was strewn, from one end to the other, with hundreds of bones, like a huge dog-kennel. The workmen wondered a little at their discovery, but, remembering that there had been a murrain among the cattle in this region some years before, they came to the conclusion that these must be the bones of cattle that had died in great numbers at that time; and, having so settled the matter to their own satisfaction, they took little heed to the bones, but threw many of them out on the road with the common limestone. Fortunately, a gentleman, living in the neighborhood, whose attention had been [pg 343] attracted to them, preserved them from destruction; and a few months after the discovery of the cave, Dr. Buckland, the great English geologist, visited Kirkdale, to examine its strange contents, which proved indeed stranger than any one had imagined; for many of these remains belonged to animals never before found in England. The bones of Hyenas, Tigers, Elephants, Rhinoceroses, and Hippopotamuses were mingled with those of Deer, Bears, Wolves, Foxes, and many smaller creatures. The bones were gnawed, and many were broken, evidently not by natural decay, but seemed to have been snapped violently apart. After the most complete investigation of the circumstances, Dr. Buckland convinced himself, and proved to the satisfaction of all scientific men, that the cave had been a den of Hyenas[4] at a time when they, as well as Tigers, Elephants, Rhinoceroses, etc., existed in England in as great numbers as they now do in the wildest parts of tropical Asia or Africa. The narrow entrance to the cave still retained the marks of grease and hair, such as one may see on the bars of a cage in a menagerie against which the imprisoned animals have been in the habit of rubbing themselves constantly, and there were marks of the same kind on the floor and walls.
It was evident that the Hyenas were the lords of this ancient cavern, and the other animals their unwilling guests; for the remains of the latter were those which had been most gnawed, broken, and mangled; and the head of an enormous Hyena, with gigantic fangs found complete, bore ample evidence to their great size and power. Some of the animals, such as the Elephants, Rhinoceroses, etc., could not have been brought into the cave without being first killed and torn to pieces, for it is not large enough to admit them. But their gnawed and broken bones attest, nevertheless, that they were devoured like the rest; and probably the Hyenas then had the same propensity which characterizes those of our own time, to tear in pieces the body of any dead animal, and carry it to their den to feed upon it apart.
While Kirkdale Cave was evidently the haunt of Hyenas chiefly, other caverns in Germany and France were tenanted in a similar manner by a gigantic species of Bear. Their remains, mingled with those of the animals on which they fed, have been found in great numbers in the Cavern of Gailenreuth, in Franconia. The subjoined wood-cut shows the head of this formidable beast, which must have exceeded in size any Bear now living. [pg 344] Indeed, although there were many smaller kinds, and the other types of the Animal Kingdom in the Tertiaries seem to approach very nearly both in size and general character their modern representatives, yet, on the whole, the earlier Mammalia were giants in comparison with those now living. The Mastodon and Mammoth, as compared with the modern Elephant, the Megatherium, as compared with the Sloths of present times, the Hyenas and Bears of the European caverns, and the fossil Elk of Ireland, by the side of which even the Moose of our Northern woods is belittled, are remarkable instances in proof of this. One cannot but be struck with the fact that this first representation of Mammalia, the very impersonation of brute force in power, size, and ferocity, immediately preceded the introduction of man, with whose creation intelligence and moral strength became the dominant influences on earth.
Among these huge Tertiary Mammalia, one of those most common on the North-American continent seems to have been the Mastodon. The magnificent specimens preserved in this country are too well known to require description. The remains of the Rhinoceros occur also in the recent Tertiary deposits of North America, though as yet no perfect skeletons have been found. The Edentata, now confined to South America and the western coast of Africa, were also numerous in the Southern States during that time; their remains have been found as far north as the Salt Lick in Kentucky. But we must not judge of the Tertiary Edentata by any now known to us. The Sloths, the Armadillos, the Ant-Eaters, the Pangolins, are all animals of rather small size; but formerly they were represented by the gigantic Megatherium, the Megalonyx, and the Mylodon, some of which were larger than the Elephant, and others about the same size of the Rhinoceros or Hippopotamus. The subjoined wood-cut represents a Mylodon in the act of lifting himself against the trunk of a tree.
They were clumsy brutes, and though their limbs were evidently built with reference to powerful movements, perhaps climbing, or at least rising on their hind quarters, the act of climbing with them cannot have had anything of the nimbleness or activity generally associated with it. On the contrary, they probably were barely able to support their huge bodies on their hind limbs, which are exceedingly massive, and on the stiff, heavy tail, while they dragged down with their front limbs the branches of the trees, and fed upon them at leisure. The Zoölogical Museum at Cambridge is indebted to the generosity of Mr. Joshua Bates for a very fine set of casts taken from the Megatherium in the British Museum. They are now mounted, and may be seen in one of the exhibition-rooms of the building. Large Reptiles, but very unlike those of the Cretaceous and Jurassic epochs, belonging chiefly to the types of Turtles, Crocodiles, Pythons, and Salamanders, existed during the Tertiary epochs. The [pg 345] wood-cut below represents a gigantic Salamander of the Tertiary deposits. It is a curious fact, illustrative of the ignorance of all anatomical science in those days, that, when the remains of this reptile (Audrias, as it is now called) were first discovered toward the close of the seventeenth century, they were described by old Professor Scheuchzer as the bones of an infant destroyed by the Deluge, and were actually preserved, not for their scientific value, but as precious relics of the Flood, and described in a separate pamphlet, entitled, "Homo Diluvii Testis." Among the Tertiary Reptiles the Turtles seem to have been a very prominent type, by their size as well as by their extensive distribution. Their remains have been found both in the far West and in the East. The fossil Turtles of Nebraska are well known to American naturalists; but the Oriental one exceeds them in size, and is, indeed, the most gigantic representative of the order known thus far. A man could stand under the arch of the shield of the old Himalayan Turtle preserved in the British Museum.