GEOLOGICAL HISTORY OF HORSE 
147 
In a revision of the American Eocene horses, Mr. Granger* 
distinguishes twenty-six species, all the three genera to which 
they belong being distinct from the early horses found in 
Europe. The American Eohippus appears to be closely re¬ 
lated to the Old World Hyracotherium, while Epihippus ap¬ 
proaches Lophiotherium. We thus have a somewhat parallel 
series in the two continents. 
In the Oligocene deposits the horses are still small, some 
of them less than eighteen inches high at the withers. 
Twenty-eight species, belonging to the two genera Mesohippus 
and Miohippus, have been described by Professor Osborn.f 
Sixty more species are mentioned by Mr. GidleyJ as having 
been procured in the Miocene and Pliocene beds, and over half 
a dozen more from Pleistocene strata. Thus we Enow from 
America already about one hundred and twenty different kinds 
of fossil horses. They gradually increase in size as we pro¬ 
ceed from the older to the newer deposits. The species with 
many toes are replaced by others with fewer toes, until we 
come to the highest form of specialization in the modern 
horse. All that remains of the outer toes is a splint-bone left 
on each side of the single toe, while the teeth which originally 
possessed short crowns have now long ones. There is ap¬ 
parently a gradual evolution from smaller and simpler forms 
to larger and more complex ones, as we glance from the older 
horse remains to the recent ones. And yet not a single gradual 
transition from one genus to the other seems to be known. 
No wonder that one of our foremost palaeontologists exclaims : 
“ The supposed pedigree of the horse is a deceitful delusion, 
which simply gives us the general process by which the tri- 
dactyle foot of an ungulate can be transformed in various 
groups into a monodactyle foot in view of an adaptation for 
speed, but this in no way enlightens us on the palaeontological 
origin of the horse.”§ 
Considering the extraordinary abundance of horse remains 
in North America, and even in the south of South America, 
* Granger, W., “ American Eocene Horses,” p. 233. 
t Osborn, H. F., “New Oligocene Horses.” 
t Gidley, J. W., “Miocene and Pliocene Horses of North America.” 
§ Deperet, C. H., “ L’evolution des Mammiferes Tertiaires,” CXL., 
p. 1517. 
