These strange creatures were of many different species. Some of them must have been six or seven feet high, for their steps are as much as three feet apart, and seem to imply a creature weighing several hundred pounds. Others were not bigger than robins. Strangely enough, we have never found their bones nor the creatures on which they fed, and but for the formation of a little patch of rocks here and there we should not have had even these footprints to prove to us that such creatures had lived in the Connecticut Valley in this far-off time. [Illustration: FIG. 5. FOOT-PRINT, TURNER'S FALLS.] But these wonderful forms are less interesting than two or three little fossil jaw-bones that prove to us that in this Triassic time the earth now bore another animal more akin to ourselves, in the shape of a little creature that gave suck to its young. Once more life takes a long upward step in this little opossum-like animal, perhaps the first creature whose young was born alive. These little creatures called Microlestes or Dromatherium, of which only one or two different but related species have been found in England and in North Carolina, appear to have been insect-eaters of about the size and shape of the Australian creature shown in Fig. 7. So far we know it in but few specimens,--altogether only an ounce or two of bones,--but they are very precious monuments of the past. [Illustration: FIG. 6. DROMATHERIUM SYLVESTRE AND TEETH OF MICROLESTES ANTIQUUS.] In this Triassic time the climate appears to have been rather dry, for in it we have many extensive deposits of salt formed by the evaporation of closed lakes, of seas, such as are now forming on the bottom of the Dead Sea, and the Great Salt Lake of Utah, and a hundred or more other similar basins of the present day. [Illustration: FIG. 7. MYRMECOBIUS.] In the sea animals of this time we find many changes. Already some of the giant lizard-like animals, which first took shape on the land, are becoming swimming-animals. They changed their feet to paddles, which, with the help of a flattened tail, force them through the water. The fishes on which these great swimming lizards preyed are more like the fishes of our present day than they were before. The trilobites are gone, and of the crinoids only a remnant is left. Most of the corals of the earlier days have disappeared, but the mollusks have not changed more than they did at several different times in the earliest stages of the earth's history. [Illustration: FIG. 8. ICHTHYOSAURUS AND PLESIOSAURUS.]