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93 



UINTA SELENODONTS 



entirely uncovered and, apparently, even a portion of the corpora quadrigemina. 

 The cerebrum is pear-shaped and narrows anteriorly, abruptly so in front of 

 the temporo-sphenoidal lobes ; the latter are proportionately quite large. The 

 convolutions are very simple and take a longitudinal course. On the dorsal 

 surface of the hemisphere only two sulci are visible, one of which is the lateral 

 and the other may be the suprasylvian, though they come together in front, 

 enclosing a pyriform gyrus between them. The shape of the hemispheres is 

 quite as much like those of Leptomeryx as it is like those of Oreodon. The 

 posterior region of the brain, including the cerebellum and medulla, is very 

 long proportionately. 



The vertebral column is represented only by scattered vertebra? from all 

 the regions in a more or less favorable state of preservation and belonging to 

 numerous individuals. Only in minor details do they differ from those of 

 Oreodon. 



The atlas is very similar to that of the White River genus ; it is short 

 antero-posteriorly, but broad and with widely extended transverse processes. 

 The odontoid process of the axis is narrower and more peg-like than in Oreo- 

 don, and the other cervical vertebrae are rather longer in proportion and some- 

 what more opisthoccelous ; they all, except the seventh, appear to be perforated 

 by the vertebrarterial canal. The trunk vertebras do not offer any noteworthy 

 distinctions from those of Oreodon except that they are somewhat lighter and 

 more slender. The tail was evidently veiy long and stout. 



The fore-limb, so far as we have it, differs very little from that of Oreodon. 

 The humerus is almost exactly as in that genus, but is more slender and has 

 a much less conspicuous deltoid ridge. The ulna has a stouter shaft and the 

 radius a more slender one, but the peculiar articulations of the elbow-joint are 

 just the same in the two genera. 



The manus (Plate III., fig. 21) is somewhat less modified than in the 

 White River types, yet the difference is not great. In all the later oreodonts 

 the lunar rests entirely upon the unciform and has only a lateral contact with 

 the magnum, which has shifted beneath the scaphoid. In Protoreodon this 

 change is in an incipient stage, and the lunar still rests partially upon the 

 magnum, which is not entirely covered by the scaphoid. The trapezium is 

 better developed and the pollex is a little larger relatively than in Oreodon. 



Pelvis, femur, tibia, and fibula differ so little from those of Oreodon that 

 they require no particular description, and the pes is likewise in almost the 

 same stage of advancement, though with some significant and interesting differ- 



