[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.]

After the Trias comes a long succession of ages in which the life of the world is steadily advancing to higher and higher planes; but for a long time there is no such startling change as that which came in the passage from the coal series of rocks to the Trias.  This long set of periods is known to geologists as the age of reptiles.  It is well named, for the kindred of the lizards then had the control of the land.  There were then none of our large fish to dispute their control, so they shaped themselves to suit all the occupations that could give them a chance for a living.  Some remained beasts of prey like our alligators, but grew to larger size; some took to eating the plants, and came to walk on their four legs as our ordinary beasts do, no longer dragging themselves on their bellies as do the lizard and alligator, their lower kindred.  Others became flying creatures like our bats, only vastly larger, often with a spread of wing of fifteen or twenty feet.  Yet others, even as strangely shaped, dwelt with the sharks in the sea.