Peterson : Miocene Beds of Nebraska and Wyoming. 49 



Dinohyus hollandi Peterson. 



{Science, N. S., Vol. XXII., No. 555, pp. 211-212, 1905; No. 

 570, p. 719, 1905.) 



(Plates XVI. and XVII.) 



The chief differences which distinguish the present genus from 

 Elotherium are found in the modification of the dentition. The first 

 upper premolar is proportionately larger, and P^ is reduced antero-pos- 

 teriorly and enlarged transversely when compared with that tooth in 

 Elotherium. The deuterocone of P^ is relatively larger than in the 

 Oligocene genus. 



In the inferior dentition a change corresponding to that in the upper 

 jaw is apparent. Premolars one and two are large while premolar 

 three is of a relatively less antero-posterior diameter than in Elo- 

 therium. The crowns of the premolars are more obtusely pointed 

 than in Elotherium, and the tubercles of the molars are less distinctly 

 separated than in the latter genus. 



The zygomatic process of the jugal is much enlarged when com- 

 pared with the corresponding process of the Elotlieria from the Oligo- 

 cene in the collections of the Carnegie Museum. This process in 

 Dinohyus reaches to the glenoid cavity and assists in forming a strong 

 buttress in front of it ; while in the Oligocene genus (especially those 

 forms from the lower levels) the process is rather slender and does 

 not reach the anterior border of this articulation. 



In the American Museum of Natural History is a well preserved 

 specimen of Elotherium ingens (No. 572) from the Protoceras beds of 

 South Dakota. The zygomatic process of the jugal of this specimen 

 forms an independent downwardly directed process about 38 or 40 mm. 

 in front of the glenoid cavity, but furnishes no apparent support for 

 the condyle of the lower jaw. The broad and downwardly extended 

 process of the jugal below the orbit, which is characteristic of Elo- 

 therium is much reduced in Dinohyus. On the inferior border of the 

 mandible the anterior pair of protuberances is but slightly noticeable 

 in Dinohyus. 



More striking differences than those above given may be found in 

 the structure of the limbs and feet when these portions of the type 

 specimen shall be extracted from the matrix. It will then also be 

 carefully compared with Elotherium humerosum Cope, the large form 



