FREE INSTITUTE OF SCIENCE 



57 



UINTA SELENODONTS 



but distinct spine, which arises near the anterior border. The anterior cotyles 

 are deeply concave and are quite widely separated, both dorsally and ventrally; 

 they are notched quite deeply on the anterior border. The surfaces for the 

 axis are rather small and are placed very obliquely with reference to the me- 

 dian line. The vertebrarterial canal pierces the base of the transverse process 

 and runs but a brief course. 



The axis has a moderately elongate, broad, and depressed centrum, which 

 bears a prominent keel upon its ventral face. The articular surfaces for the 

 atlas project outward prominently beyond the sides of the centrum, but their 

 principal diameter is the vertical one ; deep notches separate the dorsal por- 

 tions of these surfaces from the neural arch. The odontoid process is mod- 

 erately elongate, peg-shaped, and bluntly pointed, but is so broad and stout 

 as to suggest that it will eventually take on the spout-like form. The trans- 

 verse process is thin and compressed, but deep vertically, and is perforated 

 by a short vertebrarterial canal. The neural canal is narrow, but rather high, 

 and the pedicels of the arch are short from before backward. The neural 

 spine is quite remarkable, forming a large, hatchet-like plate ; it is well 

 extended antero-posteriorly, especially behind the zygapophyses, and over- 

 hangs both the atlas and the third cervical, but is rather low vertically, and 

 has a strongly curved free margin. 



The lumbar vertebra which have been preserved form a series of four, 

 probably the second, third, fourth, and fifth ; they are large and strong, and 

 indicate considerable muscular power in the loins. The centra are long and 

 depressed, and the neural arches are low, but the transverse processes are 

 long, broad, and heavy, and they extend outward without much anterior cur- 

 vature, considerably resembling those of Protoceras. 



Of the fore-limb the parts preserved are the distal end of the radius and 

 an imperfect manus, associated with the skull (No. 11,225); the distal end of 

 the humerus and the proximal end of the ulna and radius of the second 

 specimen (No. 11,223), which is referred, though with some little uncertainty, 

 to the same genus and species. The humeral trochlea is intermediate in 

 character between Protylopus and Protorcodon ; it is fairly high and cylindrical 

 in form, but is divided into three portions for the corresponding facets on the 

 head of the radius. Of these, the median or intercondylar portion is convex, 

 the others concave ; the internal facet is considerably wider than the external. 

 The intercondylar ridge is much broader and more rounded than in Protylop2is, 

 but less so than in the oreodonts. The external epicondyle is small, but the 



