506 THE MAMJIALIA OF THE UINTA FOKMATION. 



of Hyra colli erium (Owen). Oroniermm* (= Lophiotherium) was based uiDon a good 

 type lower jaw ; it has the hist lower premolar like the molars ; it is identical with 

 and pi-eeedes OroJirp]ms,f which was founded upon an uncharacteristic type {0. im- 

 milus, a numbei- of loose upper molars), and was not fully defined until later upon 

 the discovery of O. agilis. Both genera are, however, synonymous with Pliolophus 

 Owen, which is defined by the last premolar being like the molars. The species, 0. 

 agilis, is however founded upon a type in which the third and fourth upper premolars 

 have two internal lobes ; it thus falls within the definition of Upihipjms.X Epihip2ms 

 is thus in turn close to Ancliilop)lms, but may be distinguished from it by the more 

 dejjressed crests and less complete union of the para- and metaconules into transverse 

 crests. Then follows Mesolrippus with three premolars like the molars, and crests 

 like those of Amchiloplms. 



There is a remarkable parallelism in the assumption of the molar pattern by the 

 premolai-s in all the perissodactyl series. "We can almost predicate of any Wasatch 

 genus, fourth premolar unlike the molars ; of any Bridger genus, fourth premolar 

 like the molai's ; of any Uinta genus, third and fourth premolars like the molars ; of 

 any "White River genus, second to fourth preraolai's like the molars. 



PERISSOD ACT YL A. 



AMYNODON. 



Numerous errors have found their way into the descriptions of the skull and 

 dentition of this genus which require correction before its affinities can be discussed. 

 There are now three skulls known which may be referred to three species. Fii'st, the 

 type Amynodon advenus Mai-sh, fi-om the Uinta beds ; second, the type of A. ( Orilio- 

 cynodon) antlquus, nobis, from the Washakie beds ; third, the type of A. intermedius, 

 spec, nov., from the Uinta. 



Prof Marsh's description of the type is as follows :§ "The skull is intermediate 

 in I'orni between that of a tapir and a rhinoceros, but the molar teeth are entirely of 

 the latter type. The premolars are all unlike the molai's, and the canines above and 

 below are very lai-ge. The incisors are small and the inner one in each jaw is lost in 

 the present adult animal. The lower canines are placed nearly horizontal, and, taken 

 in connection with the I'cst of the anterior dentition, they prove conclusively that the 

 large lower teeth usually regarded as incisors in Aceratherium * * * are really 

 canines." The number of digits is stated to be 4-3. This description is erroneous 



*Am. Jour. Sci. and Ails, Sciil., 1872, p. 217. 

 t Op. ciL, proposi'cl Sept., 1872 ; ilclined May, 187:!. 

 Ilnlvort. and Succession of Vcrl., etc., Ann;., 1877, ii. 2X. 

 § Am. .lour. Sci and Arts, Third Scr., Vol. XIV, p. 251. 



