1 8 E. M. MUSEUM MEMOIRS. 



UINTATHERIUM. 



A synopsis of the numerous species of Uintatherium (Dinoceras) will not 

 be attempted here. From numerous specimens in our collection the following 

 species has been positively identified ; 



A. No tubercle at the entrance of the valley between the lobes of the last 

 upper molar. Nasals divided by a deep groove ; slender zygomatic 

 arch. Temporal fossa not continued far behind posterior protuber- 

 ances . U. Leidianum. 



These characters distinguish it from U. robustum ' (Leidy). This individual 

 is figured in Plate 11. 



In the first Bulletin from this Museum was described another species of 

 Uintatherium, which we called U. princeps. This species is no longer recog- 

 nized as being clearly distinct. In the multiplicity of varieties that have been 

 found by different parties, there are at present no means of ascertaining how 

 far the characters upon which species are constantly based are the outcome 

 of differences of age and sex. The development and proportions of the pro- 

 tuberances especially belong to the class of cranial modifications which may 

 have been wholly subject to differences in sex. The following synopsis of the 

 species of Loxolophodon is therefore offered provisionally. 



LOXOLOPHODON. 



Nasals deeply cleft in front and much produced beyond nasal tips. Frontal 

 protuberances large and placed directly above the orbit. Foramen incisivum 

 widely cleft in front. (Occiput unknown.) L. cornutus. 



Nasals wide and less cleft. Frontal protuberances above orbit. Occiput 

 low and broad L. galeattis. 



Nasals uncleft and barely produced beyond nasal tips. Frontal protuber- 

 ances small and anterior to orbit. Occiput high and narrow . 



L. Speirianum, sp. nov* 



The two unusually fine skulls of Uintatherium and Loxolophodon in our 

 museum have afforded an admirable opportunity for a comparison of these 

 two well-determined genera of the Dinocerata. The distinguishing features of 



' Leidy. Proc. Ac. Nat. Sc., 1872, p. 169. — Cont. Ext. Vert. Faun, of Western Territories, p. 93. 

 ' Dedicated to the discoverer of the head, Mr. Francis Speir, Jr., a member of the two expeditions. 



