370 IVORY AND THE ELEPHANT
of Nebraska are fully explored and studied, they are destined to
furnish satisfactory solutions to many of the problems relating to the
Proboscidea, and it is certain that many new forms will be added to the
all the creatures which have lived, but a moiety has been preserved.
After a few years not a vestige remains of those skeletons which bleach
in the open, while the few dropped in mud and water may become buried
and mineralized. Associated with the elephant bones are the remains
of such contemporaneous creatures as the rhinoceros, camel, early
horse, giant hogs, deer, and countless smaller forms. Great predatory
beasts, such as the sabre-toothed cats and huge dogs, were their
natural enemies. The climate was favourable, and vegetation must have
been luxuriant. Quantities of petrified wood bear evidence of the
forest vegetation of the time.
the mastodon age in Nebraska, deep river and lake conditions prevailed.
The rivers which flowed in ever-varying channels deposited gravels over
broad areas. There were wide meanders, lagoons, and marshes, and large
lakes and ponds. At flood time enormous amounts of sand, gravel, and
mud were spread over the country. In periods of drought this could be
assorted more or less by wind. For this reason we often find aqueous
and aeolian deposits alternating.
of tropical animals frequented the water courses and the rich
vegetation bordering the lakes and lagoons. Many of them perished in
the water or were subsequently swept in by freshets. Buoyed by gases of
decay, their carcasses floated until deflected into some cove by wind
or water currents. They became stranded here, and their skeletons were
finally deeply buried in sand and mud.