RHINOCEROS OF NEBRASKA. 553 
In the collection of Dr. Owen are contained of R. occidentalis the following spe- 
cimens : 
1. A mutilated skull, with one series of molar teeth entire. 
2. Two fragments of lower jaws of different individuals. 
3. The distal extremity of an os femoris. 
Description of the Skull—The specimen of the skull is very much fractured, but 
those parts which are remaining still retain their original position. It has lost 
almost the entire superficies of the right side, the end of the nose, occiput, excepting 
its lower portion, and the outer portions of the molar teeth of the right side. It 
belonged to an adult but not old animal, as the permanent teeth are all protruded, 
but none of the characteristic grinding surfaces are effaced. 
Lateral view. —The side view of the skull presents its most remarkable feature in 
a striking manner, which is its great degree of straightness antero-posteriorly, when 
compared with other species. It has the appearance as if a head of the ordinary 
form of the recent Rhinoceros had been bent downwards anteriorly and posteriorly 
until it had become nearly horizontal. With a depressed condition of the back 
part of the skull, a relatively large portion of the temporal fossa is situated poste- 
rior to the root of the zygoma. 
The upper surface of the latter inclines forwards at an angle only of 15°, and 
the zygoma itself is rather more sigmoid in its course forwards than in Rhinoceros 
Indicus, and its outer surface is deep, being nearly two inches, and is moderately 
convex and nearly vertical. 
The temporal fossa has about the same relative extent as in R. Indicus, but is 
longer and has less vertical depth. Superiorly it is defined by a prominent margin 
commencing at the post-orbitar process, and coming in contact with that of the 
opposite side at the posterior part of its course, forming a double parietal crest. 
The surface of the fossa is very oblique, but for two and a half inches above the 
root of the zygoma, is convex and nearly vertical. 
The orbit is more transversely and deeply excavated, and its orifice is better 
defined than in R. Indicus. 
The supra-orbitar process is large, prominent, convex, and rough, and partially 
overhangs the inferior margin of the orbit. 
The face is relatively longer than in R. Indicus, and therefore very much more 
so than in Acerotherium incisivum. 
From a fragment of the left intermaxillary bone remaining in the specimen, it 
may be determined to be large and strong, but the notch of the anterior nares is 
relatively small. 
The maxillo-intermaxillary suture is strongly serrate, and reaches within a half 
inch of the naso-maxillary suture. 
Superior view.—The upper surface of the head is remarkable on account of its 
great breadth at the forehead, and its narrowness posteriorly. It is a slightly 
depressed plane, prominent at the posterior extremity, as constituted by the double 
parietal crest, but is most elevated above the forepart of the orbits. 
The upper surfaces of the nasal bones incline towards each other in the specimen, 
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