ave fossils of animals belonging to modern
families--rhinoceroses, camels, deer, dogs, cats, horses--but the genera
of which are now extinct. The Pliocene strata (above the Miocene)
contains fossils of animals so closely related to the wild animals now
on the earth as to belong to the same genera. They differ from modern
kinds only in the species, as the red squirrel is a different species
from the gray.

So the record in the rocks shows a gradual approach of the mammals to
the kinds we know, a gradual passing of the mighty forms that ruled by
size and strength, and the coming of forms with greater intelligence,
adapted to the change to a colder climate.

It sometimes happens that a farmer, digging a well on the prairie,
strikes the skeleton of a monster mammal, called the _mastodon_. This
very thing happened on a neighbour's farm when I was a girl, in Iowa.
Everybody was excited. The owner of the land dug out every bone, careful
that the whole skeleton be found. As he expected, the director of a
museum was glad to pay a high price for the bones.

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

Restoration of an aquatic Dinosaur, _Brontosaurus excelsus_, from the
Upper Jurassic and Lower Cretaceous of Wyoming. The animal in life was
over 60 feet long]

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

Restoration of the small carnivorous Dinosaur, _Ornitholestes hermanui_,
catching a primitive bird _Archaeopteryx_. Upper Jurassic and Lower
Cretaceous]

The mastodon was about the size of an elephant, with massive limbs, and
large, heavy head that bore two stout, up-curved tusks of ivory. The
creature moved in herds like the buffalo from swamp to swamp; and old
age coming on, the individual, unable to keep up with the herd, sank to
his death in the boggy ground. The peat accumulated over his bones,
undisturbed until thousands of years elapse, and the chance digging of a
well discovers his skeleton.

Frozen in the ice of northern Siberia, near the mouths of rivers, a
number of mammoths have been found. These are creatures of the elephant
family, and belonging to the extinct race that lived in the Quaternary
Period, just succeeding the Tertiary. The ice overtook the specimens,
and they have been in cold storage ever since. For this reason, both
flesh and bones are preserved, a rare thing to happen, and rarer still
to be seen by a scientist.

The ignorant natives m