554 



RHINOCEROS OF NEBRASKA. 



probably more than natural, for they are fractured from their connexions, although 

 there appears to be but little displacement. 



There is no roughness or elevation upon the forehead, or rise forwards upon the 

 nose, as far as the position of the second molar tooth, indicating the possession of a 

 horn by the animal, and it therefore probably belongs to the subgenus Acerothe- 

 rium, Kaup, although the face, instead of being decreased in length, as in the latter 

 in its relation with the true Rhinoceros, is even increased, as before stated. 



Posterior view. — The back part of the head is too much broken to gain much 

 information in the details of its character. It appears to have been relatively 

 narrow, but very much bulging posteriorly, so that the portion forming the upper 

 boundary of the foramen magnum overhangs the latter considerably posterior to its 

 inferior margin. 



Inferior view. — (Tab. ix., fig. 1.) In the specimen the right condyle of the occi- 

 put and the lower internal portion of the left are broken away, but in the remainder 

 of the latter it is very perceptible that the condyles have a much more vertical 

 position than in R. Indicus. 



The basilar process is narrow, the distance between the anterior condyloid fora- 

 mina being only one inch. 



The foramen ovale is distinct from the foramen lacerum, and is placed on a line 

 just in advance of the post-glenoid tubercle. 



The latter is relatively short and broad in comparison with that of R. Indicus. 



The glenoidal surface is relatively greater antero-posteriorly in comparison with its 

 breadth than in the species last mentioned. It also presents a little more outward, 

 and at its most external posterior portion is more depressed. 



The hard palate in the specimen is considerably fractured, but all the parts 

 appear to have remained perfectly in position. It is very narrow and very much 

 arched, especially anteriorly. The teeth in a nearly straight line upon each side 

 converge anteriorly, being distant between the anterior lobes of the last molars 

 twenty-two lines, and between the first of the series only nine lines. 



Inferior maxilla. — Of the two fragments of the lower jaw in the collection of Dr. 

 Owen, one broken into two of the left side, contains the posterior two molars, and 

 part of the one preceding, the other fragment, also, of the left side contains the third 

 to the fifth tooth inclusive. Both belonged to adult individuals, but the only ana- 

 tomical characters to be gained from the fragments, exclusive of the teeth, are the 

 depth of the lower jaw, which is twenty-eight lines below the last molar, and the 

 thickness, which is fourteen lines. 



Dentition. — The superior molars (Tab. ix., fig. 1) are about one-third smaller 

 than those of Acerotherium incisivum, and also bear considerable resemblance to 

 them in their form. 



They all possess a basal cingulum, which is, however, but feebly developed on 

 the outer side of the anterior half of the fifth and sixth molars, and is obsolete on 

 part of the internal lobes of the same teeth. Upon the premolars, from the second 

 to the fourth inclusive, the basal ridge is very strongly developed. 



The posterior molar, as in Acerotherium incisivum, exhibits no tendency to form a 



