I go 2.] Osborn, Oligocene Titanotheres . 99 



LEVEL NOT RECORDED 



Megacerops avus Marsh. — This type jaw, distinguished 

 by the presence of three lower incisors, belongs to a much 

 larger animal than M. brachycephalus. The presence of 

 an outer lower incisor may be due to reversion or to the 

 retention of a milk tooth ; all young Titanotheres have three 

 milk incisors. The formula, I3, P3, does not appear suffi- 

 cient to remove this type generically, because the form of the 

 canine, shape of the jaw, feeble development of the cingulum, 

 etc., lead to placing it in Megacerops. 



M. coloradensis Leidy. — Horns of medium length, of rela- 

 tively slender cylindrical section. Nasals elongate, decurved, 

 and narrow anteriorly. This is the type species. 



M. angustigenis Cope. — Type in Ottawa Museum. Horns 

 as in M. coloradensis, but nasals abbreviated and expanding 

 anteriorly. 



M. ? selwynianus Cope. — Level not recorded, probably 

 Middle Beds. Type in Ottawa Museum. Nasals extremely 

 narrow, elongate, with highly arched inferior surface as in 

 the species next to be described. 



MIDDLE BEDS. 



Megacerops bicornutus, sp. no v. ' 



Type No. 1476, cotype No. 108 1, Amer. Mus. Horns directed an- 

 teriorly. Homlets upon the inner and anterior mid-portion of the 

 horn. Basal section of the horn slightly oval, subtrans verse. Nasals 

 narrow and relatively elongate. Sharp malar bridge in front of orbit. 

 Orbit large. 



This animal stands nearest M. selwyniaims, although dis- 

 tinguished by the greater size and Flightly greater width of 

 the nasals. The sharp malar bridge is the most absolute 

 character. The two hornlets are possibly variations. 



UPPER BEDS. 



Megacerops tichoceras Scott & Osborn. — Type skull in 

 Harvard Museum. This is distinguished from M. dispar by 



