DAKOTA AND NEBRASKA. 115 



tooth, indeed, looks as if it might pertain to a distinct genus, though I rather incline 

 to believe its j^eculiarity is an extreme variation of an individual character. 



An accompanying fragment of the maxilla, containing the premolars and the 

 greater part of the first true molar, exhibits these teeth of the same form as those of 

 the preceding specimens, but more worn. 



An upper canine presents a more robust character than those of the first-described 

 sjjecimeus. Just above the limit of its posterior worn surface it measures eight lines 

 from before backward and nine lines from side to side. 



An inferior lateral incisor is represented in figures 6 and 7, plate X. Its summit 

 is worn from contact with the incisor above, and its postero-internal border by con- 

 tact with the upper canine. Its internal face is bounded by a strong basal ridge. 

 The length of the crown, in its present worn, blunted condition, is nuie lines ; its 

 transverse diameter at base ten Unes ; and from without inwardly it is four and a 

 half lines. 



The fragment of a malar bone below the infra-orbital margin is nearly two inches 

 in depth. 



The fragment of a nasal bone, consisting of the anterior portion, presents this 

 terminating in a blunt point, relatively much shorter than in Oreodon. Its breadth 

 is eleven lines. 



3. A pair of slightly worn premolars and an incisor from a third individual 

 younger than either of those to which the preceding specimens belonged. The 

 former teeth, represented in figure 9, are the second and third premolars of the right 

 side. The incisor, figure 8, is the upper lateral one of the same side. 



MERYCHYUS. 



The extinct genus Merychyus is indicated by specimens discovered by Dr. Hayden, 

 during Warren's Expedition of 1857. They were found in the sands of the Niobrara 

 River, are well preserved, and have no adherent matrix. They are regarded by Dr. 

 Hayden as belonging to the pliocene formation, or bed F of his section, as indicated 

 on pages 16 and 20. 



Merychyus is closely related to Oreodon and Merycochoerus, though distinguished 

 from both by well-marked characters. The number, relative position and general 

 form of the teeth are the same as in those genera. See plate XI. 



The true molars are constructed on the same plan as those of all other ruminants, 

 recent and extinct, and are intermediate in their character with those which have 

 short crowns as in the Deer and Oreodon, and those which have long crowns as in 

 the Camel and Sheep. See figures 1, 2, 12, 13, 15, plate XI. 



In comparison with the true molars of Oreodon the crowns are considerably longer 



