80 ON THE EXTINCT MAMMALIA OF 



Oreodon Culbertsoni. 



The most abundant remains of Oreodon, from the Mauvaises Terres of White 

 River, as previously mentioned, are referable to a species of intermediate size, to 

 which the above name has been given in honor of Messrs. Alexander and Thaddeus 

 A. Culbertson, who were among the first to collect specimens from, and direct the 

 attention of naturalists to the rich fossil bone deposits of Dakota. 



The skull of Oreodon Culbertsoni, figure 1, plate VI, figure 2, plate VII, is rather 

 smaller than that of the domestic Sheep or the Collared Peccary. Different specimens 

 exhibit considerable variation in size, and also in the relative proportion of parts, 

 including the teeth. 



The greater number of specimens of skulls and parts of the same, of smaller size 

 and graceful proportions, are supposed to indicate females. Specimens of larger size 

 and more robust proportions are supposed to have belonged to males. Specimens of 

 the smallest size approach those of the smallest species of Oreodon, but retain other 

 characters distinguishing them as appertaining to 0. Culbertsoni. Some specimens, 

 in comparison with the more common forms, exhibit a disproportion of parts. There 

 are large skulls with comparatively small teeth, and small skulls with comj>aratively 

 large teeth. 



Skulls of Oreodon Culbertsoni differ more or less in every particular. They differ 

 in the length and strength of the sagittal crest, in the prominence of the forehead, in 

 the exact form and proportionate size of the orbital entrance, in the depth and rela- 

 tive breadth of the lachrymal fossa in advance of the orbit, and in the height, 

 breadth, and exact form of the face. 



The sagittal crest in Oreodon Culbertsoni gradually continues as an uninterrupted 

 linear ridge to the frontal bone, but in some specimens of crania, especially in some 

 of those supposed to pertain to the female skulls, it expands into a long narrow tri- 

 angle, with a more or less deeply notched base receiving the pointed summits 

 together of the frontals. 



The lachrymal fossa^ or the hemispheroidal pit in advance of the orbital entrance, 

 is almost large enough to receive the end of a finger, and is always more strictly 

 confined to the lachrymal bone than the corresponding depression in the Sheep, Hog 

 and Peccary. It usually occupies nearly the whole facial surface of the lachrymal 

 bone, and not unfrequently includes a small portion of the maxillary. Sometimes it 

 is narrower or more contracted and deeper, at other times it is shallower than usual 

 without being proportionately wider. 



The nasal bones of Oreodon Culbertsoni vary in their proportionate breadth and 

 transverse convexity in different skulls. Usually the posterior extremities together 



