126 PROCEEDINGS OF THE NATIONAL MUISEUM. vol.58. 



would probably not have been wider. The inner face of the hinder 

 lobe of S. promptus is considerably more flattened than in S. aus- 

 tralis. The parastyle of the latter appears to be less prominent than, 

 in S. promptus. Also, the outer face of the anterior lobe of S. aus- 

 tralis is not so deeply excavated as in the tooth from Afton ; so that 

 in the former the rib on the middle of the face stands out beyond the 

 parastyle; in the Afton species, not so far as the parastyle. It may 

 be noted that the two teeth compared are worn down almost exactly 

 the same amount. 



Besides the upper tooth, there is preserved a part of an atlas (Cat. 

 No. 9121) wdiich is referred provisionally to this species. It is quite 

 unlike the same bone in Bison and resembles that of Ovibos. The 

 atlas of Ovibos differs from that of Bison in being of heavier con- 

 struction, almost all parts of the bone being thicker than the cor- 

 responding parts in Bison. Below the spinal canal the atlas from 

 Afton is 44 mm. thick; in Bison, 35 mm. On each side there is a. 

 broad and deep notch at the outer end of the cavity for the cor- 

 responding occipital condyle; in Bison this is absent or of trifling 

 depth. The spinal canal is smaller than in Bison. In Ovibos there 

 is, in front of and just below the spinal canal, a median tuberosity 

 that is not present in Bison. The cavities for the occipital condyles 

 are not so deep as in Bison. 



In the fossil atlas the arches are missing and the bone has been 

 eroded. In general the vertebra agrees with that of Ovibos; but the 

 hinder end of the spinal canal measures transversely about 50 mm.y 

 instead of 40 mm., as in Ovibos. The anteroposterior extent of the 

 bone in the midline below is 67 mm.; in Ovibos, only 46 mm. The 

 lateral extent of the bone was originally 200 mm. or more. 



The cervical vertebra (pi. 8, figs. ^6) is regarded as being the 

 fifth. The neural spine is eroded off, as well as the transverse proc- 

 esses. The bone has so many points of agreement with the cor- 

 responding one of Ovibos vioschatus that the relationship is un- 

 doubted. The anterior articular end of the centrum is similarly con- 

 vex; the hinder one similarly concave. As in Ovibos, the foramina 

 for the vertebrarterial arteries are reduced in diameter. In the ver- 

 tebra at hand the foramina have a diameter of only 4 mm. They 

 are on a level with the floor of the spinal canal; in Ovibos much 

 below this position. The height of the centrum, from the floor of 

 the spinal canal to the lower surface in front, is 61 mm. ; the width, 

 taken at the level of the spinal canal is 92 mm.; the length, taken 

 between the centers of the two ends, 54 mm. The spinal canal 

 is oval, 30 mm. high and 24 mm. wide. 



The dorsal vertebrae appear to have belonged near the front of the 

 series, but they are so extensively damaged that exactitude can not 

 be attained. There is so much difference in size that they may have 



