221 



A strong bulge projects from the middle of the anterior lobe into the valley 

 of the crown, which is not so well developed in 11. occidentalism and a second 

 bulge at the bottom of the valley is absent in the latter. The basal ridge is 

 stronger in front, and internally at the entrance of the valley of the crown it 

 forms two conspicuous, rounded tubercles not seen in a corresponding posi- 

 tion in R. occidentalis. The presence of these tubercles, however, is, perhaps, 

 merely an individual peculiarity. The tooth measures 15 lines antero-p'oste- 

 riorly and internally, and is estimated to have been 19 lines transversely. 



The lower-jaw fragment, containing a molar, represented in Fig. 9, Plate 

 II, exhibits nothing peculiar distinguishing it from the corresponding part 

 either of R. occidentalis or R. hesperius. 



Rhinoceros pacificus. 



The fossil specimens indicative of the second species of rhinoceros from 

 the Oregon Tertiary consist of a mutilated right side of the upper jaw with 

 portions of fangs of the molars, except of the first premolar, and several iso- 

 lated molar teeth. 



The specimens indicate a species larger than the preceding, but not reach- 

 ing Rhinoceros crassus of the Niobrara Tertiary, which was about the size of 

 the existing India rhinoceros. 



The upper-jaw specimen retains portions of the fangs of six molar teeth, 

 counting from behind. The space occupied by the back two premolars and 

 the molars is estimated at nearly 1\ inches; that occupied by the true molars 

 at rather more than 5 inches. 



The fore part of the zygomatic space is on a line with the fore part of the 

 last molar tooth. 



Fig. 6, Plate II, represents an upper molar which is supposed to belong to 

 this species. The specimen is broken at its back part, and is labeled "Alkali 

 Flat." The crown at the fore part measures 21 lines in diameter, and is esti- 

 mated to have measured \\ inches antero-posteriorly. The bottom of the 

 crown is embraced with a strong basal ridge, which is strougest anteriorly 

 and internally. The inner lobes expand inwardly, but do not bulge in the 

 abrupt manner posteriorly to the same degree that they do in R. occidentalis. 

 The bottom of the oblique valley of the crown is expanded, and is compli- 

 cated by the projection into it of four folds. 



Another tooth, represented in Fig. 7, Plate II, likewise labeled "Alkali 



