IQ02.] Osborn^ Oiigocene Titaiiotheres. IO3 



bicornntns as a member of a collateral phylum distinguished 

 by internal hornlets. In such case Diploclonus may prove to 

 be a valid subgenus. 



Phylum III. 



Medium-sized Titanotheres with long horns placed more di- 

 rectly above the orbits, of deep anteroposterior diameter at the 

 base, oval at tip ; connecting crest feeble or wanting. Nasals 

 thin; sktdl proportion varying in the species. Incisors degen- 

 erate. Canines very small, approximated. 



Genus SYMBORODON Cope. 



Syn., Anisacodon, Diconodon Marsh. 



This genus is characterized from the types of S. torvus, S. 

 acer in the American Museum, and of 5. montanus in the 

 Yale and National Museums. It is known only from the 

 Middle and Upper Beds, but is entirely distinct. It agrees 

 with Titanotherium in the disappearance of incisor teeth, 

 but differs from it absolutely in the horn and nasal struc- 

 ture. It is also widely separate, both in cutting teeth and' 

 horn structure, from Megacerops and Brontotherium. 



PROBABLY UPPER BEDS. 



Symborodon torvus Cope. — Brachycephalic, incisors ^, 

 nasals thin, buccal processes of zygomata broad and flat, 

 occipital pillars broad. 



Symborodon acer Cope (Syn., 5. altirostris Cope). — Dol- 

 ichocephalic, nasals thicker, abbreviated. Horns of male long, 

 recurved, low connecting crest, incisors vestigial. 



MIDDLE AND UPPER BEDS. 



Symborodon montanus Marsh. — Type in Yale Museum. 

 Nasals thin, of medium length, upper incisors vestigial. 



