1902.] Osborn, Oligocene Titanotheres. lOI 



incisors resemble those in Brontothermm rather than in M. 

 robiistus. 



Fig. 6. Megacerops marshi. (Amer. Mus. Nat. Hist. No. 501 ; jaw No. 516.) Type. 

 This skull was figured by Osborn (1896, p. 181) as Tiianotheriutn irigonoceras. 



Megacerops robustus Marsh. — Type in Yale Museum. 

 Numerous skulls in the American, Princeton, and National 

 Museums. Recorded by Hatcher from very summit of the 

 Upper Beds. In skull development this represents an 

 extreme evolution of the M. hrachycephalus-M . dispar 

 series. It is, however, distinguished from M. dispar by 

 the presence of diastemata behind the canines, retarded 

 development of the tetartocones on the superior premo- 

 lars, broadly transverse horn-section, procumbent position 

 of the horns. 



The above-described new species, M. (? Diploclonus) bicor- 

 nutiis, from the Middle Beds is possibly a connecting form 

 between Megacerops and the aberrant species from the Upper 

 Beds termed Diploclonus ampins by Marsh. The latter is 

 distinguished by short, divergent horns of peculiar triquet- 

 rous section, with incisors \, and elongate canines flattened 

 posteriorly. The animals called Allops are certainly inore 

 closely related to Megacerops than to either Titanotherium, 

 Symborodon, or Brontotherium, but their phyletic position is 

 uncertain. 



