[Illustration]

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