138 DISTRIBUTION OF EXTINCT ANIMALS. [PART Il. 
Mexico: Meniscotherium, having resemblances to Palewosyops, 
Hyopotamus, and the Limnotheride ; Phenacodus, the size of a 
hog, of doubtful position, but perhaps near Hlotherium ; and 
Achcnodon, as large as a cow, but more hog-like than the pre- 
ceding. Another new genus from the Miocene of Colorado— 
Pelonax—is said by Professor Cope to come between Elotherium 
and Hippopotamus. 
The Camelide are very abundant, and form one of the most 
striking features of the ancient fauna of America. Procamelus, 
Homocamelus, and Megalomeryx, are extinct genera found in the 
Pliocene formation; the first very closely allied to the Old 
World camel, the last smaller and more sheep-like. In the 
Miocene two other genera occur, Pebrotherium and Protomeryz, 
the former allied to both the camel and the lama. 
Deer are represented by a single species of Cervus in the 
Pliocene, while two extinct genera, Leptomeryx and Merycodus, 
are found in the Miocene deposits, the latter indicating a tran- 
sition between camels and deer. Two other genera, Hypisodus 
and Hypertragulus, of very small size, are said by Professor 
Cope to be allied to the Tragulide and to Leptomeryx. 
The Bovide, or hollow-horned ruminants, are only represented 
in the Newer Pliocene by a single species of an extinct genus, 
Casoryx, said to be intermediate between antelopes and deer. 
We now come to an exclusively American family, the Oreo- 
dontide, which consisted of small animals termed by Dr. Leidy, 
“ruminating hogs,” and which: had some general structural 
resemblances to deer and camels. They abounded in North 
America during the Pliocene, and especially during the Miocene 
epoch, no less than six genera and twenty species having been 
discovered. Merychus contains the Pliocene forms; while 
Oreodon, Eporeodon, Merychocherus, Leptauchenia, and Agrio- 
cherus are Miocene. The last genus extends back into the 
Eocene period, and shows affinity to the European Anoplothe- 
ride of the same epoch. 
Proboscidea.—The Elephantide are only represented in 
America by one species of Mastodon and one of LHlephas, in 
the Newer Pliocene deposits. In the Older Pliocene, Miocene, 
