DAKOTA AND NEBRASKA. 73 



expressed than when it is called a genus of ruminating hogs. From the comparative 

 abundance of its remains we may suppose it to have existed in great numbers, and to 

 have lived together in large herds, which once roamed over the extensive prairies 

 and through the dense forests of ancient Nebraska, as the Peccaries do in our own 

 times in South America. 



The species of Oreodon exhibit a considerable range of variation in size, in the 

 proportion of parts and in the details of form, and extreme varieties of each more or 

 less closely approximate one another. A few specimens referred to one or other of 

 the species present such differences as to leave it doubtful whether they have been 

 properly placed, the imperfection of the fossils usually rendering the determination 

 uncertain. 



The sl<ull of Oreodon, in its general form and construction, approximates that of its 

 more ancient relative, the AnoplotJierium of the eocene deposits of Europe. In the 

 usual side-view it bears a general resemblance to that of the Peccaries, and many of 

 its details of form and construction indicate a relationship of Oreodon with these 

 animals. 



Without the lower jaw, the skull of Oreodon has a decidedly wolfish aspect. 

 Indeed, in the shape of the cranium, the form and extent of the temporal fossjB, 

 separated by a well-developed sagittal crest, and in the form of the face, with the 

 almost continuous row of teeth, Oreodon presents a more striking resemblance to a 

 Wolf than it does to any of the existing members of its own order. 



Among living ruminants, in the form and construction of the cranium and temporal 

 fossse, Oreodon most nearly approaches the Camel family. The form of the face is 

 very unlike that of any living ruminant. The orbits are closed behind by a post- 

 orbital arch, as in the order generally, and large lachrymal fossae exist in front of 

 them, as in the Deer and the extinct Bootherium. 



The lower jaw approximates in form that of the Peccary, 



Like AnoplotJierium, Oreodon is remarkable for the completeness of its dentition. 

 As in the former, it possesses forty-four teeth, arranged in series almost as continuous, 

 being only broken to an extent sufficient to allow the passing and accommodation of 

 the points of the upper and lower canines. 



The true molar teeth of Oreodon are constructed after the same characteristic plan 

 of those of all other ruminants, living and extinct, and therefore serve to fix the 

 immediate relationship in classification of the genus. 



Description of the shull. — The skulls of the different species of Oreodon are to some 

 extent of variable size and general robustness, and also in the relative proportion of 

 their different parts. (Plates vi, vii, viii.) 



The side-view of the skull presents a triangular outline, as in the Peccary, but is of 



less proportionate depth posteriorly, and therefore slants less above. 



10 



