32 Annals of the Carnegie Museum, 



Marsh. The postorbital processes on the frontal and jiigal are of large 

 size, in this respect unlike Titanotherium. The postorbital process on 

 the frontal of the latter genus is usually located further back and is much 

 smaller in proportion. The external poition of the glenoid cavity is 

 preserved in No. 2858, and is somewhat less convex in the antero- 

 posterior diiection than in the latter genus. As in Titanotherium the 

 anterior palatine foramina aie small round openings, which in the 

 present genus are situated further back from the alveolai boider of 

 the incisors. The palate is of the deep concave form usually met with 

 in the Titanotheres, and the posterior narial opening extends approxi- 

 mately as far forward as in the Oligocene genus, reaching to the pos- 

 terior portion of M-. 



That the type of the skull was saddle-shaped is very evident from 

 the material under study, but whether or not the characteristically 

 broad superioi aspect of the parietals and the heavy and broad occiput 

 seen in Titanotherium had been attained to the same degree as the 

 similarity of the anterior region in the two genera suggests might have 

 been the case, will not be completely known until the posterior region 

 of the skull of the Uinta representatives of this phylum is found. It 

 is highly probable that the similarity presented by the anterior 

 region will be preserved throughout the cranium, which will then 

 reveal more exactly the features of a true titanothere than was 

 anticipated. From the type of Protitanotherium emarginatum at 

 Princeton University, Hatcher® was apparently able to determine 

 that the sagittal crest is absent, and that the dorsal surface of the 

 skull is probably slightly concave antero-posteriorly. 



Mandible. 

 Plate VII. 

 The lower jaw is somewhat depiessed by crushing, but allowing for 

 this fact, it appears that the horizontal ramus of Diploceras osbonii is 

 shallowei than in P. emarginatum. Characteristics which may further 

 be noted, aie: the more rounded under surface of the symphysis, 

 and the constriction of the lower jaws in the area between the canine 

 and the premolars which is gi eater than in P. emarginatum. As in 

 the latter, the symphysis is strong and the mental foramen is large, 

 located well down on the ramus, directly below P^. The lower jaw 

 is broken off back of M . 



* The American Naturalist, Vol. XXIX, 1895, p. 1085. 



