hippus Marsh, and are all of diminutive size, hardly larger t 
' in many respects, much more indeed than any other a 
. species, but instead of the single toe on each foot, so characteris! 
FOSSIL HORSES IN AMERICA. 
BY PROFESSOR O. C. MARSH. 
o M d 
Ir is a well known fact that the Spanish discoverers of America 
found no horses on this continent, and that the modern horse — 
(Equus caballus Linn.) was subsequently introduced from the old — 
world. It is, however, not so generally known that these animals — 
had formerly been abundant here, and that long before, in Ter- — 
tiary time, near relatives of the horse, and probably his ancestors, — 
existed in the far west in countless numbers, and in a marvellous a 
variety of forms. The remains of equine mammals, now known — 
from the Tertiary and Quaternary deposits of this country, already : 
represent more than double the number of genera and species: 5 
hitherto found in the strata of the eastern hemisphere, and hence ~ 1 
afford most important aid in tracing out the genealogy of the i 
horses still existing. oe 
The animals of this group which lived in this country during the 3 
three divisions of the Tertiary period were especially numerous in 
the Rocky Mountain regions, and their remains are well preserved 
in the old lake basins which then covered, so much of that country. 7 
The most ancient of these lakes— which extended over a Com- 
siderable part of the'present territories of Wyoming and Utah— ; 
remained so long in Eocene times that the mud and sand, slowly — 
deposited in it, accumulated to more than a mile in vertical thick: 
ess. In these deposits, vast numbers of tropical animals were 
entombed, and here the oldest’ equine remains occur, four species 
of which have been described. These belong to the gan 
f the horse 
fox. The skeleton of these animals resembled that 0 
of all modern equines, the various species of Orohippus had “ 
toes before and three behind, all of which reached the ground. 
The skull, too, was proportionately shorter, and the orbit was N 
enclosed behind by a bridge of bone. There were forty-four 107 
in all, and the premolars were smaller than the molars. - The 
crowns of these teeth were very short. The canine teeth wer 
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