bones of the foot indicate a different kind
of horse--an unknown species. But in the main features, the skeleton is
distinctly horse-like.

In rocks of deeper strata the fossil bones of other horses are found.
They differ somewhat from those found in rocks nearer the surface of the
earth, and still more from those of the modern horse. The older the
rocks, the more the fossil horse differs from the modern. Could you
think of a more interesting adventure than to find the oldest rocks that
show the skeletons of horses?

The foot of a horse is a long one, though we think of it as merely the
part he walks on. A horse walks on the end of his one toe. The nail of
the toe we call the "hoof." The true heel is the hock, a sharp joint
like an elbow nearly half way up the leg. Along each side of the cannon,
the long bone of this foot, lies a splint of bone, which is the remnant
of a toe, that is gradually being obliterated from the skeleton. These
two splints in the modern horse's foot tell the last chapter of an
interesting story. The earliest American horse, the existence of which
is proved by fossil bones, tells the first chapter. The story has been
read backward by geologists. It is told by a series of skeletons, found
in successive strata of rock.

The "Bad Lands" of the arid Western States are rich in fossil remains of
horses. Below the surface soil lie the rocks of the Quaternary Period,
which included the drift laid down by the receding glaciers and the
floods that followed the melting of the ice-sheet. Under the Quaternary
lie the Tertiary rocks. These comprise three series, called the Eocene,
Miocene, and Pliocene, the Eocene being the oldest. In the middle region
of North America, ponds and marshy tracts were filled in during the
Tertiary Period, by sediment from rivers; and in these beds of clay and
other rock debris the remains of fresh-water and land animals are
preserved. Raised out of water, and exposed to erosive action of wind
and water, these deposits are easily worn away, for they have not the
solidity of older rocks. They are the crumbly Bad Lands of the West, cut
through by rivers, and strangely sculptured by wind and rain. Here the
fossil horses have been found.

_Eohippus_, the dawn horse, is the name given a skeleton found in 1880
in the lower Eocene strata in Wyoming. This specimen lay buried in a
rock formation ages older than that in which the oldest known skeleton
of this family had been found. Its