DAKOTA AND NEBRASKA. 107 



two species of Oreodon, the 0. Culhertsoni and 0. gracilis, but by far the greater 

 number belong to the former species. The fragments chiefly consist of portions of the 

 long bones of the extremities, for the most part the articular ends, while vertebrte 

 are comparatively rare. The specimens are almost alwaj's isolated, and only in a few 

 instances have they been preserved in contiguity, or in their proper relative position 

 in masses of the rock to which they belong. Nearly all the mammalian fossils from 

 Dakota and Nebraska, which form the subject of the present work, are specimens 

 which have been picked up from the surface of the locality in which they were found, 

 and they mostly consist of single bones or fragments, weathered from the neighboring 

 cliflfs. Rarely do the specimens consist of several bones, except in the case of the 

 skulls, held together in their jaroper relative position. None of the fossils have as yet 

 been quarried from the rocks in which they abound. Hence, notwithstanding the 

 enormous quantity of remains of Oreodon which have been obtained, we have not 

 procured sufficient material to build up an entire skeleton. 



Vertebrce. — I have had the opportunity of examining two specimens, consisting of 

 the cervical series of vertebrae of Oreodon Galbertsoni. These are partially imbedded 

 together, with portions of the skulls in masses of matrix, but the exposed parts are 

 much broken. The more perfect of the two series is seven and a quarter inches long, 

 and the individual vertebrae, so far as can be ascertained in their imperfect state, in 

 shape are much like those in ordinary ruminants in general, or like those in the Hog 

 and Peccary, The atlas measures two inches ten lines transversely, and three-fourths 

 of an inch between the articular processes in front and behind. The transverse pro- 

 cesses are obliquely convex at the lateral border, as in the Deer, but are relatively 

 not so much prolonged posteriorly. 



The bodies of the succeeding five vertebrae are strongly carinated inferiorly, as in 

 living ruminants. The spinous processes successively increase in length from the 

 third to the last. The axis measures an inch and a half in length, from the summit 

 of its odontoid process, and an inch and a third transversely between the anterior 

 articular processes. Its spinous process is broad and strong, and shaped as in recent 

 ruminants. 



A series of the bodies of the anterior eight dorsal vertebrte, partially imbedded in 

 the mass of matrix in contiguity with the less perfect cervical series above mentioned, 

 is six and three-quarter inches in length, the body of the eighth being nine and a half 

 lines long. Their form and construction, so far as can be seen, are not different from 

 what they are in recent ruminants and suilline animals. 



A series of three bodies of anterior lumbar vertebrae of 0. Culhertsoni, adhering to 

 a portion of matrix, measures three inches and a tliird in lengtli, each vertebral body 

 being a little over an inch long and three-fourths of an inch transversely at the pos- 



