552 



R II I N C E 11 S 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 individual as the portion of lower jaw, consists 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 externally, as in Pala^otherium 

 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 Pala}otherium 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. 



Roth 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 occidcntcalis : Proc. Acad. Nat. Sci., vol. v., p. 119; ib., 270. 

 Acerotlicrium occideiitale : ib., p. 331. 



The species was at first established upon several fragments of teeth, and after- 

 wards coufinncd by obtaining several entire teeth. 



