138 DISTRIBUTION OF EXTINCT ANIMALS. [part ii. 



Mexico : Meniscotherium, having resemblances to Palccosyops, 

 Hyopotamus, and the Limnotheridie ; Phenacodus, the size of a 

 hog, of doubtful position, but perhaps near Motherium ; and 

 Achmnodon, as large as a cow, but more hog-like than the pre- 

 ceding. Another new genus from the Miocene of Colorado — 

 Pclonax — is said by Professor Cope to come between Elotheriurn 

 and Hippopotamus. 



The Camelidse 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, Poebrotherium and Protomeryx, 

 the former allied to both the camel and the llama. 



Deer are represented by a single species of Ccrvus in the 

 Pliocene, while two extinct genera, Leptomeryx and Mcrycodus, 

 are found in the Miocene deposits, the latter indicating a tran- 

 sition between camels and deer. Two other genera, Hypisodus 

 and Hypertracjulus, of very small size, are said by Professor 

 Cope to be allied to the Tragulidse and to Leptomeryx. 



The Bovidse, 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- 

 dontidw, 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. Mcrychus contains the Pliocene forms ; while 

 Oreodon, Eporeodon, Merychochcerus, Zeptauchcnia, and Agrio- 

 chcerus are Miocene. The last genus extends back into the 

 Eocene period, and shows affinity to the European Anoplothe- 

 ridtB of the same epoch. 



Proboscidea. — The Elephantidse are only represented in 

 America by one species of Mastodon and one of Elephas, in 

 the Newer Pliocene deposits. In the Older Pliocene, Miocene, 



