THE EVOLUTION OF THE ELEPHANT
leaves and twigs. The shovel-teeth were no longer needed. The long lower jaws were no more an advantage. So we come to a series of elephants in which the lower jaw is shortening. The necessity for reaching the ground, at least for water, still remains, and for this purpose the long upper lip is used, but being no longer supported it becomes pendant, a proboscis. These new forms with a shortened lower jaw are the mastodons. There are many intermediate stages, such as Mastodon longirostris of the lower Pliocene of Germany, in which the lower jaw is still of considerable length. Mastodon atticus from Pikerni, in Greece, has a long chin, and while young has incisors in the lower jaw. Throughout the Pliocene there are several species of mastodons in Europe and Asia. By Pleistocene time they had reached North America, where they flourished throughout the Ice-Age and for a short time afterward. Among even the American mastodons there is occasionally found one which has vestiges of tusks in the lower jaw, like the one at Amherst College, which has tusks nine inches long.
The upper tusks, after they were no longer used for digging, did not disappear, as would be expected, but instead turned upward and forward, increasing in size, so that those of a well-grown adult are usually seven to eight feet long, and a single tusk weighs over a hundred pounds. Projecting so far in front of the animal they may be of some use in pushing or lifting, perhaps in fighting; but these uses can hardly compensate for the inconvenience of such projections, or for the effort involved in carrying so much weight out in front of the head. Like the antlers of the elk or moose, they seem to be overdeveloped structures, and were probably among the features that caused the extermination of these great beasts. Though the mastodons flourished throughout the Pleistocene epoch and for a short time thereafter, they all
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