80 RHINOCEROS. ‘ 
I was at one time disposed to consider the two species of Nebraska Rhinoceros as 
having belonged to the subgenus Aceratherium, 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 Blainville (Ost. Gen., Rhin., Pl. IX.), (who regards the Acera- 
therium incisivum 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 afford a firm basis to a nasal horn. On the con- 
trary, in both species of Nebraska Lhinoceros, 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 gpecies of Nebraska Rhinoceros re- 
semble the Aceratheriwin incisivum 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 /2hinoceros, 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. 
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