Scott and Osborn.] ^^^ [Sept. 2, 



Professor Marsh kindly allowed lis to do, we were formerly led to con- 

 sider the Bridger species as a distinct genus- {Orthocynodon). 



The numerous specimens from the Uinta formation now in the Prince- 

 ton collection show that Ortliocynodon is very probably identical with 

 Amynodon. The premolars are not all unlike the molars, as the third and 

 fourth of the upper premolar series have all the molar elements, but are 

 somewhat smaller ; the incisors are present in their full number in the 

 upper jaw; the lower canines are not procumbent but fully erect. We 

 can therefore confirm Professor Marsh's statements only with regard to 

 the pattern of the molar teeth and probably also as to the number of 

 digits. 



Amynodon advenus Marsh is the only species as yet known from the 

 Uinta beds, in which, especially in the higher strata, it is very abundant. 



Diplacodon elatus Marsh. f — This animal, the largest yet known from 

 the Uinta, is of especial interest as being intermediate between the Cha- 

 litherioids of the Bridger (Palceosyops, Leurocephalus, etc.), and the gigan- 

 tic MenodontldcB of the White River, as was first suggested by Professor 

 Marsh. The dentition is like that of Palceosyops, but the premolars have 

 commenced to assume the molar pattern ; there are, however, no traces 

 of the horn-like processes so characteristic of Menodus. The skeleton, 

 which is very fully represented in the collection, is massive, and in many 

 respects closely like that of Menodus. The cervical vertebrse are short, 

 with opisthoca3lous centra and quite long spines ; the dorsal vertebrse are 

 heavy and in the anterior region have very long spines, which, however, 

 do not reach the extreme length found in Menodus; the lumbars are 

 rhinocerotic in character ; the ribs are long, flattened and heavy. The 

 scapula is, like that of Menodus, very rhinocerotic, long and narrow, but 

 with more abruptly rising spine and rudimentary metacromion ; the 

 humerus is very massive, with strongly developed deltoid hook and supin- 

 fitor ridge ; this humerus is a somewhat reduced copy of that of Menodus; 

 the ulna is stout for its entire length and has a very prominent olecranon ; 

 the radius diflfers in no essential except size from that of Menodus ; the 

 carpus is low and broad, the metacarpals and phalanges like those of 

 Palceosyops, only stouter. The pelvis is like that oi Palceosyops, with long, 

 pedunculate and plate-like ilium, which is not everted nearly so much as 

 in Menodus, and long, heavy and trihedral ischium ; Ihe femur is long 

 and massive, with very prominent third trochanter, and with the rotular 

 trochlea narrower and deeper than in Mtnodus ; the tibia is shorter than 

 the femur ; the calcaneum has a very long tuber calcis and a narrow 

 cuboidal facet, considerably narrower than in Palceosyops ; it appears also 

 to possess the distinct fibular facet which is found in Menodus ; the astrag- 

 alus is broader and shallower than in Palceosyops, and has a more exten- 



* Bull. E. M. Museum, No. 3, pp. 1 et seq. 



fAm. Jouru. Sci. and Arts, 3d Ser,, Vol. ix, p. 24C. Introd. and Succ. Vert. Life, 

 p. 27. 



