142 ON THE EXTINCT MAMMALIA OP 



River, presented to the Academy of Natural Sciences in 1846 by Mr. Alexander 

 Culbertson, a gentleman engaged in the western fur trade. It was the first of the 

 mammalian fossils brought to the notice of the author from the great bone deposito- 

 ries of Dakota. Notwithstanding the rich yield of fossils from the same region, but 

 few remains of the same species have since been obtained that have come under my 

 inspection. 



The specimen was first described in the Proceedings of the Academy, in 1847, and 

 subsequently in " The Ancient Fauna of Nebraska," in which it is well represented, 

 together with the teeth, in figures 1 — 4, plate i. 



The fossil retains the greater part of both jaws, the intermediate portion of the 

 face, portions of the orbits, and part of the base of the cranium, together with the 

 auditory bullae. It belonged to an individual which had not yet reached maturity, 

 for though all the permanent true molars had protruded, the temporary molars had 

 not been shed. 



■ The upper portion of the face, including the forehead and nasals, is broken away, 

 as is also the case with the premaxillaxies and the anterior extremity of the lower 

 jaAY. 



The remaining portion of the face in the fossil is long, narrow and tapering. 

 From the anterior margin of the orbit it slopes forward and inward without being 

 impressed by a lachrymal fossa. Near its middle, however, above the prominent 

 alveolar border, and below the position occupied by the nasals, it is deeply depressed 

 into a fore-and-aft oval concavity, the bottom of which reaches within a couple of 

 lines of that of the opposite side. The depression to some degree may be the result 

 of accident, though it has not that appearance in the fossil. At its fore part is a 

 rather abrupt bulge, extending forward to the broken end of the specimen, which 

 apparently is due to the existence of a canine alveolus like that of the male Musk 

 Deer. 



The orbit appears to have possessed the usual large size observed in recent rumi- 

 nants. Its anterior margin, somewhat everted, is on a line with the middle of the 

 anterior half of the second upper true molar tooth. The inferior margin, directed 

 obliquely downward and forward, is slightly everted, while the malar surface beneath 

 is almost vertical instead of being strongly inclined downward, as in recent ruminants 

 generally. 



The zygoma pursues an oblique course downward and forward to the face. Its 

 outer surface is comparatively deep in proportion to the size of the skull. 



The infra-orbital foramen opens about an inch in advance of the orbit, over the 

 position of the fore part of the last temporary molar tooth. 



The facial surface of the lachi-ymal is oblong-square, and contributes to the general 

 slope of the contiguous portion of the face. At the orbital margin it is produced into 



