26 U. S. P. R. R. EXP. AND SURVEYS—ZOOLOGY—GENERAL KEPORT. 
the former, however, occurring abundantly also as a fossil genus, in America as well ag the Old 
World. The teeth differ much from those of the other families, in the constant absence of canines, 
and of lower incisors in any but very young animals. 
2. Genuina. The members of this family are distinguished from the Proboscidea by the absence of the elongated, prehensile 
nose; and by the existence of small canines, instead of the enormous tusks, as well as of incisors in both jaws. The feet are 
three or four toed, with hoofs of unequal size, the limbs are short, the body, neck, and head more elongated, The body is 
usually full and rounded, the skin very thick and naked ; the nose and ear flap much developed. 
The living genera of this family are Zapirus, Rhinoceros, Hippopotamus, and, according to 
Giebel, Hyrax. The most important of the fossil are Palaeotherium, Titanotherium, Anchi- 
therium, Lophiodon, Anthracotherium, &c., many of these with North American representatives. 
3. Suina. Animals of comparatively small size. More compressed body, pointed head, large ears, blunt snout, slender, 
thin legs ; hoofs arranged in pairs, and the skin covered with rather close bristly hairs. 
The living genera of this family consist of Sus, Dicotyles, Poreus and Phacochoerus, the fossil 
chiefly of Entelodon, Choeropotamus, Hyopotamus, Hyotherium, Adapis, &c., nearly all with 
North American representatives in the bone beds of the Mauvaises Terres. ‘ 
The genus Sus embracing the common hog is characterized by having four-toed feet, and in 
being without any gland on the back or fleshy lobes on the face. Dicotyles, with two species, 
one of them the common Peccary of Texas, has differently constituted canines, but three toes on 
the hind feet, a very rudimentary tail, and a peculiar gland on the back. 
The genus Porcus, with the well known Babyroussaas its type, is chiefly characterized by its 
enormous canines, which curve upwards and outwards in a large semicircle. 
The remaining genus, Phacochoerus, or wart hog, has the minimum number of incisor and 
molar teeth in the family, four-toed feet, four fleshy lobes on the face, large tusks, and a com- 
pressed and powerful body. 
4. Toxodontidae. This family and the next, 5. Anoplotheridae, are composed entirely of extinct genera and species, some of 
which belong to our continent, the Toxodontidae, indeed, restricted to South America. It is in the Anoplotheridae that we find 
the transition from the Pachydermata to the Ruminantia. 
It is much to be regretted that in his account of the fossil genera and species of the Pachyder- 
mata, Giebel should have entirely lost sight of the numerous species from North America, so 
ably and satisfactorily defined by Dr. Leidy. 
