The Evolution of {he Horse. 
117 
Rhinoceroses were at one time abundant in North America, but 
at the present day they are confined to Africa and the southern 
parts of Asia. They are all animals of large size but of little 
intelligence, generally timid in disposition, though ferocious 
when attacked and brought to bay, using their nasal horns as 
weapons, by which they strike and toss their assailants. Their 
sight is dull, but their hearing and scent are remarkably acute. 
They feed on herbage, shrubs, and leaves of trees, and, like so 
many other large animals which inhabit hot countries, sleep the 
greater part of the day, being most active in the cool of the 
evening, or even during the night. They are fond of bathing 
and wallowing in water or mud. As with the tapirs, none of 
the species have been domesticated. 
The horse family are the most progressive members of the 
group, having undergone a more complete series of changes, in 
many parts of their structures, than either of the others — modi- 
fications all in adaptation to a changed mode of life. All the 
existing members of the group inhabit open plains, prairies, 
steppes, or deserts. They save themselves from their enemies, 
the larger carnivora, not by hiding among the recesses of 
thickets, as the tapir, or by their great size and strength, as 
the rhinoceros, but by the acuteness of their senses of sight, 
smell, and hearing, and by their marvellous speed. Their limbs 
are eminently adapted for galloping over hard ground, not for 
plodding deliberately through swamps ; and their teeth are 
admirably modified for masticating the harsh, dry herbage of 
the plains, not the soft, succulent vegetables of the marshes and 
forests, in which their ancestors mainly dwelt. 
The existing species of the genus Equus, or horse, are the 
following : — 
(1.) The horse (Equus caballus), distinguished from all the 
others by the long hairs of the tail being more abundant, and 
growing quite from the base, as well as from the end and sides, 
and also by possessing a small, bare callosity on the inner side of 
the hind leg, just below the hock, or heel-joint, in addition to the 
one on the inner side of the fore-arm, above the carpus ("knee-" 
joint), common to all the genus. The mane is also longer and 
more flowing, the ears shorter, the limbs longer, the toes broader, 
and the head smaller. Fossil remains of horses differing but 
slightly from the smaller and inferior breeds of those now existing 
are found abundantly, in deposits of the most recent geological 
age, in almost every part of America, from Eschscholtz Bay in 
the north to Patagonia in the south. In that continent, however, 
they became quite extinct, and no horses, either wild or domesti- 
cated, existed there at the time of the Spanish conquest, which 
