358 O. C. Marsh— Vertebrate Life in America. 
were several distinct species. ‘They were the largest mammals 
animals nearly equaled the Klephant in size, but had shorter 
limbs. The skull was armed with two or three pairs of horn- 
cores, and with enormous canine tusks. ‘The brain was propor- 
tionally smaller than in any other land mammal. The feet had 
five toes, and resembled in their general structure those of (o- 
ryphodon, thus indicating some affinity with that genus. These 
mammals resemble in some respects the Perissodactyles, and in 
others the Proboscidians, yet differ so widely from any known 
Ungulates, recent or fossil, that they must be regarded as form- 
ing a distinct order, the Dinocerata. Only three genera are 
known, Dinoceras, Tinoceras and Uintatherium, but quite a num- 
ber of species have been described. During the later part of the 
middle Hocene, these animals were very abundant for a short 
time, and then became extinct, leaving apparently no succes- 
sors, unless possibly we have in the Proboscidians their much 
modified descendants. Their genetic connection with the 
Coryphodonts is much more probable, in view of what w 
now know of the two groups. 
this Continent, and was told in reply that the reports to that 
effect were too unsatisfactory to be presented as facts in science. 
This remar me, on my return, to examine the subject 
myself, and I have since unearthed, with my own hands, not less 
than thirty distinct species of the horse tribe, in the Tertiary 
deposits of the West alone; and it is now, I think generally 
admitted that America is, after all, the true home of the Horse. 
can offer you no better illustration than this of the advance 
vertebrate paleontology has made during the last decade, or 0 
the important contributions to this progress which our Rocky 
Mountain region has supplied. 
The oldest representative of the horse. at present known, is 
the dirninutive Hohippus from the lower Eocene. Several spe- 
cies have been found, all about the size of a fox. Like most 
of the early mammals, these Ungulates had forty-four teeth, 
the molars with short crowns, and quite distinct in form from 
