gQ RHINOCEROS. 



I was at one time disposed to consider the two species of Nebraska Rhinoceros dife 

 having belonged to the subgenus Aceratlierium, Kaup, from the fact that in one of 

 the specimens, upon which the larger species was established, the upper part of the 

 face as far forward as the position of the second molar tooth, presents no indica- 

 tion of an advancing rise to produce a prominence or boss at the end of the nose 

 for the support of a horn. In the specimens of the smaller species, the face is too 

 much mutilated to obtain any idea of its form, but from the resemblance of the 

 back part of the cranium and the lower part of the face to those of the larger 

 species, I supposed the similarity probably continued in the remainder of the face, 

 and thus indicated the species to be of the same subgenus as the other. Upon 

 more mature reflection, I am inclined to think both species of Rhinoceros of Ne- 

 braska possessed a horn upon the end of the nose, for although this portion of the 

 face is not preserved in any specimens to determine the fact, yet the construction 

 of the remaining portion of the face is more after the type of that of the true 

 Rhinoceros than that of the Aceratherium. In this, according to the representation 

 by Kaup (Fig. 2, Tab. X. of the Ossem. Foss.), the lateral notch of the anterior 

 nares extends as far back as the commencement of the fifth molar tooth ; or, as 

 represented by De Blaiuville (Ost. Gen., Ehin., PI. IX.), (who regards the Acera- 

 tlierium inclsivum as the female of the Rhinoceros incisivus, Cuvier, with which the 

 name is synonymous), as far as the fourth molar tooth, thus leaving little width to 

 the face from this point to the orbit, and a feeble support to the nasal bones from 

 the ossa maxillaria, necessary to aflford a firm basis to a nasal horn. On the con- 

 trary, in both species of Nebraska Rhinoceros, the lateral notch of the nares does 

 not extend beyond the position of the first molar tooth, thus producing a great de- 

 gree of relative breadth to the face, and an ample support laterally to the nasal 

 bones, so as to enable them to sustain the horn, which probably tipped the nose. 

 Both species of Nebraska Rhinoceros, at most, were unicorn, for the forehead is 

 slightly depressed and smooth, and presents neither boss, elevated roughness, nor 

 other indication of the existence of a frontal horn. 



In the form of the upper molar teeth, the species of Nebraska Rhinoceros re- 

 semble the Acerutheriuvi incisioum more than they do recent species of Rhinoceros, 

 especially in the existence of a well-developed basal ridge on the inner side of the 

 premolars. 



In the smaller species of Nebraska Rhinoceros, incisor teeth existed in both jaws 

 in the adult, as indicated in two specimens by small remaining fragments of the 

 fangs, and it is probable that they also existed, under the same circumstances, in 

 the larger species, although this is proved only for the upper jaw, one of the speci- 

 mens of which yet preserves a portion of an incisive alveolus in the intermaxillary 

 bone. 



