552 RHINOCEROS OF NEBRASKA. 
cavities, bounded internally by a thick, obtuse ridge, descending from the elevated 
ends of the crescents. The basal ridge externally is well developed, and is less 
deep at the intervals than at the middle of the lobes. 
The third lobe of the last lower molar (Tab. ix., fig. 3) has a thick, acute ridge, 
bounding the cavity upon the inner side of the triturating surface. 
The molars undergo a rapid reduction in size anteriorly, for the last molar mea- 
sures a little over four inches antero-posteriorly, the first true molar twenty-two lines, 
and the third premolar only seventeen lines. 
The latter tooth (Tab. xii., B, 7), presents the same form as the true molars. 
The crown of the inferior canine (Tab. xii. B, 8) is curved conoidal, nineteen 
lines long, and one inch broad at the base. It presents a strongly developed basal 
ridge internally, which has a feeble disposition to continue externally. The tip 
of the crown and its antero-external side for half an inch in the specimen have 
the enamel worn off. 
The fragment of an upper molar (Tab. xii., B, 6), considered to belong to the 
same sadeirinal as the portion of lower jaw, skate of a conical protuberance of 
the inner side of the grinding surface. The remaining fragments of upper molars 
are single outer lobes. ‘These are deeply concave adetasensilly, as in Palseotherium 
magnum, and have a narrow basal ridge. (Tab. xii., B, 3, 4. 
All the preceding specimens, except, probably, the latter two, I suspect belong 
to a different genus from either Paleotherium or Anchitherium, and should the 
suspicion prove correct, Titanotherium would be a good name for the animal, as 
expressive of its very great size. 
RHINOCEROS. 
Two species of Rhinoceros are indicated as having existed in the ancient fauna of 
Nebraska, by its fossil remains. One was about three-fifths the size of the existing 
Rhinoceros Indicus, and the other was very small, not being a great deal larger 
than the common Hog. 
Both species have been characterized in the Proceedings of the Academy of 
Natural Sciences, the former under the name of Rhinoceros occidentalis, the 
latter with that of R. Nebrascensis. 
RHINOCEROS OCCIDENTALIS.  Leidy. 
(Tab. ix., figs. 1, 2.) 
Rhinoceros occidentalis: Proc. Acad. Nat. Sci., vol. v., p. 119; ib., 276. 
Acerotherium occidentale: ib., p. 831 
The species was at first established upon several fragments of teeth, and after- 
wards confirmed by obtaining several entire teeth. 
