EVOLUTION OF THE HORSE 7 
continental glaciers covered the northern parts of Europe and 
North America, and the Recent Epoch, of more moderate climate 
during which civilization has arisen. 
In the early part of the Quaternary Period, wild species of 
Horse were to be found on every continent except Australia. 
Remains of these true native horses have been found buried in 
strata of this age in all parts of the United States, in Alaska, in 
Mexico, in Ecuador, Brazil and Argentina, as well as in Europe, 
Asia and Africa. All these horses were much like the living spe- 
cies and most of them are included in the genus Equus. A 
complete skeleton of one of them (Equus scottr) found by the 
American Museum expedition of 1899 in Northern Texas, is 
mounted in the large wall-case. The difference between it and 
the Domestic Horse (see framed diagram of modern horse skel- 
eton) is chiefly in proportions, the skull shorter with deeper jaws, 
the legs rather short and feet small in proportion to the body. 
In these characters this fossil horse resembles an overgrown 
zebra rather than a domestie horse. We know nothing of its 
coloring. It may have been striped, and in this case would have 
been very zebra-like; but there are some reasons for believing 
that it was not prominently striped. The bones are petrified, 
brittle and heavy, the animal matter of the bone having entirely 
disappeared and having been partly replaced by mineral matter. 
They are not much changed in color, however, and are so per- 
fectly preserved that they look almost like recent bone. 
All the remains of these native horses which have been found 
in America have been petrified more or less completely; this 
means that they have been buried for many thousands of years, 
for petrifaction is an exceedingly slow process." It serves as an 
easy method of distinguishing them from bones of the Domestic 
Horse, found buried in the earth. These cannot in any case 
have been buried for more than four or five centuries, and have 
not had time to petrify. 
Remains of these fossil horses from various parts of the 
United States are shown in the counter-case. One very rich 
* The so-called petrifaction which occurs in some hot springs, coating 
objects dipped into them with a white, stony coat of lime is not true petrifaction. 
In true petrifaction the substance of the bone is replaced particle by particle 
with mineral matter. 
