COPE.] PALEONTOLOGY MIOCENE PEEIOD. 463 



nera in Colorado. The Poeirotlterium, rather rare in Dakota, is quite 

 abundant in Colorado. On the other hand, no trace of the Titanothe- 

 rium of the former has yet been announced from the latter locality, and 

 it is probable, indeed, as remarked by Professor Marsh, that that genus 

 is characteristic of another horizon of the Tertiary from the one under 

 consideration. If, as I believe, the Colorado Miocene is the true White 

 Eiver epoch, then the Titanofheriumis derived from another.* Comj)ara- 

 tively few traces of the Symhorodons have yet been brought from Da- 

 kota, but this may be due to the fragility of these fossils and local causes. 

 The differences in the carnivora are not strikingly great ; the only genus 

 not in some degree representative in the two faunas being the Bunoclu- 

 rus of the present paper. 



The most important result obtained by the expedition of 1873 was 

 the discovery of an abundant fauna of iacerti^ia and Ophidia and of 

 the smaller mammalia of the insectivorous and rodent orders. A genus 

 of supposed Quadrumana was discovered, and an elucidation of the 

 structure of the genus of gigantic, horned perissodactyles, which I called 

 Synihorodon, was rendered possible by the large amount of material ob* 

 tained. While the pre-eminently horned type of the present fauna is the 

 order of Uuminantia^ and it has been found that those of the Eocene 

 period were an aberrant type of proboscidians, those of the Miocene are 

 now shown to be perissodactyles. 



The predecessors or ancestors of the hog, BaMrussa, and similar exist- 

 ing animals, are being gradually brought to light by modern paleonto- 

 logical studies. One of those nearest the domesticated form has been 

 found in the Miocene of France, and is referred to the genus Pakeocha:- 

 rtis. It is also related to the peccaries, which appear to have existed 

 during the same early period in North America in considerable abund- 

 ance. Their existence in South America at the present time is one of 

 many indications that that region has not advanced in respect to its 

 fauna as rapidly as our own and the old continents. Another Miocene 

 genus of hogs is the Elotlierium, which has left remains in France and 

 in North America. The common species of the Nebraska beds is the E. 

 mortonii of Leidy, which was as large as a pig. Its front teeth are much 

 developed at the expense of the hinder ones ; and it had bony tuberosi- 

 ties on the under jaw in the positions now supporting wattles in the 

 hog. I discovered during the past season much the largest species of 

 Elotlierhim yet known. The skull was longer than that of the Indian 

 rhinoceros, and the tuberosities of the lower jaw were greatly developed. 

 The front x^air formed divergent branches on the lower front of the chin, 

 so that it appeared to bear a horn on each side, which the animal, doubt- 

 less, found useful in rooting in the earth. The species was semi-aquatic 

 in its habits, like the Hippopotamus and Dinotheriuni ; but while these 

 are furnished with extraordinary developments of the lower incisor- 

 teeth for tearing u^) their food, the Elotherium ramosnni is the only 

 animal known which possessed horns in the same position and for the 

 same purpose. 



A still^older type of hogs — which may claim to be the predecessor in 

 structure as well as in time of all known genera— is the Achamodon, 

 Cope, from the Eocene of Wyoming, described a few pages back. The 

 A. insolens was a powerful beast, larger than a boar, with a compara- 



* I formerly Hupposed, following Dr. Leidy, tliat Tit another ium is cLaractoristic of the 

 horizon of Oreodoi), &c., and therefore quoted Professor Marsh as assigning- a different 

 age to the Colorado beds. Onre-examinatiou of his remarks, (Amer. Jonrn. Sei, Arts, 

 1670, p. 292,) while they bear this interpretation, 1 believe that ho did not intend to 

 make any direct assertion to this effect. 



