F. B. Loo i rds — HhinocerotidcB of the Lower Miocene. 55 



placed that on a partly worn tooth they actually join and the 

 intervening valley between the protoloph and the metaloph is 

 interrupted. The crochet is only incipient ; and the crista, 

 while wide, is not prominent. The cingulum is well developed 

 in front and behind, but internally is wanting except for a 

 trace between the protocone and hypocone. 



Diceratherium nanum Marsh. 



This Journal, vol. ix, p. 243, 1875. 



The type is ^N"o. 10,004 in the Yale Museum from the John 

 Day Eiver in eastern Oregon. The specimen is the front of a 

 skull including the upper and lower incisors, the lower canines 

 and the first three upper and lower premolars ; all however 

 worn to the roots, so that the dental pattern is obliterated, and 

 the only available character is size. In this it agrees closely 

 with D. annectens. 



Fig. 4. Diceratherium nanum M.; incisor and first three upper premolars 

 of the type, one-half nat. size. 



Diceratherium hesperium Leidy. 

 Proc. Acad. Nat. Sci., Phila., p. 176, 1865. 



The type in this case is a lower molar from the John Day of 

 Oregon.^ Later to this, Leidy assigned some further frag- 

 mentary material, in which was a third upper molar, which is 

 so far the only distinctive specimen. The lower molar used as 

 type is intermediate between D. armatum and D. annectens, 

 and while it will never be certain that the assigned specimens 

 are the same species, there seems to be a distinct species of this 

 size, which they may well typify. The features of the third 

 upper molar* are that the protoconule and the metacone are 

 much swollen, and there is a small tubercle in the valley 

 between the protocone and the hypocone. 



Diceratherium pacificism Leidy. 

 Proc. Acad. Nat. Sci., Phila., p. 248, 1871. 



This type is again fragmentary material from the John Day 

 of Oregon. Here the first molar tooth described is a second 

 upper molar from the right side, which indicates a well marked 

 * See Rep. U. S. Geol. Surv. Terri., vol. i, pi. ii, fig. 8. 



