In
the _Rhinoceros megarhinus_ (fig. 249, B), on the other hand, no
such partition exists between the nostrils, and the nasal bones
are greatly developed in size. It was a two-horned form, and is
found associated with _Elephas meridionalis_ and _E. Antiquus_ in
the Pliocene deposits of the Val d'Arno, near Florence. Like the
preceding, it survived, in diminished numbers, into the earlier
portion of the Post-Pliocene period.
[Illustration: Fig. 249.--A. Under surface of the skull of
_Rhinoceros Etruscus_, one-seventh of the natural size--Pliocene,
Italy.; B, Crowns of the three true molars of the upper jaw, left
side, of _Rhinoceros megarhinus_ (_R. Leptorhinus_, Falconer),
one-half of the natural size--Pliocene, France. (After Falconer.)]
The Horses (_Equidoe_) are represented, both in Europe and America,
by the three-toed Hipparions, which survive from the Miocene,
but are now verging upon extinction. For the first time, also,
we meet with genuine Horses (_Equus_), in which each foot is
provided with a single complete toe only, encased in a single
broad hoof. One of the American species of this period (the _Equus
excelsus_) quite equalled the modern Horse in stature; and it
is interesting to note the occurrence of indigenous horses in
America at such a comparatively late geological epoch, seeing
that this continent certainly possessed none of these animals
when first discovered by the Spaniards.
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