E IT I N C E R S OF N E B R A S K A. 553 



In the collection of Dr. Owen are contained of R. occidentalis the following spe- 

 cimens : 



1. A nmtihitcd skull, -with one scries of molar teeth entire. 



2. Two fragments of lower jaws of different individuals. 

 o. The distal extremity of an OS femoris. 



Description of the Shidl. — The specimen of the sknll 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 arc effaced. 



Lateral view. — The side view of the skull presents its most remarkable feature in 

 a striking manner, which is its great degree of straightncss antero-posteriorly, when 

 compared with other species. It has the appearance as if a head of the ordinary" 

 form of the recent Rhinoceros liad 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 forw^ards 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 defnied 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 lialf 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 nuich 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 withiu a half 

 incli of the naso-maxillary suture. 



Superior vieio. — 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. 



Tlie upper surftices of the nasal bones incline towards each other in the specimen, 



