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This lower jaw seemed incomprehensible, almost a monstrosity until it occurred to me that it exactly corresponds to the elongated upper lip and nose which we call the elephant's trunk and that the trunk of "Tetrabelodon" must have rested on his long lower jaw.
And, in fact, we are conducted through a series of changes of form by ancient elephant-like creatures which are of older and older date as we pass along the series, and are known as Mastodon, Tetrabelodon, Palæomastodon, Meritherium, until we come to something approaching the general form of skull and skeleton and the typical dentition of the early mammalian ancestor.
Photographs, casts, and actual specimens of the extraordinary skull of the long-jawed mastodon or Tetrabelodon and of the creatures mentioned below may be seen in the Natural History Museum. Lastly we have the wonderful series of discoveries made about twelve years ago by Dr.
In descending to Tetrabelodon we leave behind us the elephants with hanging unsupported trunk; the lower jaw here is of sufficient length to support the great trunk. When the lower jaw shortened in the later mastodons and elephants the trunk did not shorten too, but remained free and depending, capable of large movement and of grasping with its extremity.
Then the land rose, and the elephant passed by the new tracts into the north. Its next representative, Tetrabelodon, is found in Asia and Europe, as well as North Africa. The frame is as large as that of a medium-sized elephant, and the increase of the air-cells at the back of the skull shows that an increased weight has to be sustained by the muscles of the neck.
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