DAKOTA AND NEBRASKA. 127 



The last premolar nearly resembles that o^ Meri/chi/us and Oreodon, but difiers in 

 the internal median ridge, which is simple and extends obliquely backward, and does 

 not i3roject an offset forward as in the former genera. The anterior premolars 

 resemble those of the latter genus, in a less well-developed condition. 



The crown of the caiiiue is proportionately thicker in comparison with its breadth 

 than in Menjcliijus or Oreodon, and the internal ridge is more prominent, so as to 

 make the crown appear more decidedly trihedral than in the latter genera. The 

 incisors are like those of the latter. 



Leptauchenia decora. 



The species distinguished by the above name was the first noticed, and that upon 

 which the genus was originally proposed. It was established before the discovery of 

 Merycoclioerus and Merycliyus, and was indicated by some small fragments of jaws with 

 molar teeth, which, from their resemblance to those of the Auchenia or Lama, gave 

 rise to the name oi Leptnuchenia. A number of additional fragments, including a 

 mutilated skull, all from near Eagle Nest Butte, on the White River, serve to give us 

 a better acquaintance with the anatomical characters of the species. 



Lepfawc7ie/«'a c/eco?'rt was rather smaller than Oreodon gracilis. The skull, judging 

 from a crushed and somewhat distorted specimen, represented in figure 6, plate XII, 

 has a rather more compact form than that of the latter, being proportionately 

 broader, shorter, and, independently of the mandible, lower. 



The cranium is like that oi Lept(%uclienia major, but appears proportionately to have 

 been deeper and less wide. The face appears to have been proportionately shorter 

 and broader, and its fore part appears to have been remarkably shortened. 



The forehead is like that of L. major. The vacuities of the face did not extend so 

 deeply into the frontals as in the latter, and the prolongation of the forehead sejia- 

 rating them was proportionately much shorter. The ant-orbital processes articulating 

 with the lachrymals are wider than in L. major. Large lachrymal fossge exist as in 

 the latter, and the infra-orbital foramen occupies a corresponding position above the 

 third premolar. The supra-orbital foramen occupies a corresponding position to those 

 in L. major. 



The infra-orbital arch as formed by the malar is of remarkable robustness. It 

 projects more outwardly and is more than half as deep again than in the larger 

 Oreodon gracilis. 



The lower part of the face, if the condition in the specimen is not the accidental 

 result of crushing, is of remarkable breadth and is proportionately short. The sides 

 of the upper jaw are unusually convex outwardly, and the teeth appear crowded in 

 position. The upper true molars form a strong convexity downwardly, while the 

 premolars in advance present a concavity in the same direction. 



