ico Canon, South Dakota]

[Illustration: _By permission of the American Museum of Natural History_

Opalized wood from Utah]

[Illustration: _By permission of the American Museum of Natural History_

Restoration of a carnivorous Dinosaur, Allosaurus, from the Upper
Jurassic and Lower Cretaceous of Wyoming. When erect the animal was
about 15 feet high]

The fish-reptile, _Ichthyosaurus_, was a hump-backed creature, thirty to
forty feet long, with short neck, very large head, and long jaw, set
with hundreds of pointed teeth. Its eye sockets were a foot across. The
four short limbs were strong paddles, used for swimming. The long,
slender tail ended in a flat fin. Perfect skeletons of this creature
have been found. Its rival in the sea was the lizard-like
_Plesiosaurus_, the small head of which was mounted on a long neck. The
tail was short, but the paddles were long and powerful. No doubt this
agile creature held its own, though somewhat smaller than the more
massively built Ichthyosaurus.

The land reptiles called _Dinosaurs_ were the largest creatures that
have ever walked the earth. In the American Museum of Natural History,
in New York, the mounted skeleton of the giant Dinosaur fairly takes
one's breath away. It is sixty-six feet long, and correspondingly large
in every part, except its head. This massive creature was remarkably
short of brains.

The strangest thing about the land reptiles is the fact that certain of
them walked on their hind legs, like birds, and made three-toed tracks
in the mud. Indeed, these fossil tracks, found in slate, were called
bird tracks, until the bones of the reptile skeleton with the bird-like
foot were discovered. Certain long grooves in the slate, hitherto
unexplained, were made by the long tail that dragged in the mud.

When the mud dried, and was later covered with sediment of another kind,
these prints were preserved, and when the bed of rock was discovered by
quarrymen, the two kinds split apart, showing the record of the stroll
of a giant along the river bank in bygone days.

The flying reptiles were still more bird-like in structure, though
gigantic in size. Imagine the appearance of a great lizard with
bat-like, webbed wings and bat-like, toothed jaws! The first feathered
fossil bird was discovered in the limestone rock of Bavaria. It was a
wonderfully preserved fossil, showing the feathers perfectly. Three
fingers of each "hand" were free and clawed, so that the cre