164 BULLETIN OF THE 



there were other species both smaller and larger. This animal was about 

 eight feet high at the shoulder, and over twelve feet long. The height is 

 greatly increased by the extraordinary development of the spines of the 

 anterior dorsal vertebrae. These are well preserved, and in two cases com- 

 plete to the tip, in the materials at our disposal. They are broad and flattened 

 nearly to the tip, so as to fit closely together. The neck is longer than that 

 of Uintatherium, but shorter than that of the rhinoceros. With the power of 

 flexing the elbow, the head could readily be lowered to the ground in feeding. 

 The arm, fore-arm, and shoulder-blade are decidedly rhinocerotic in character, 

 although showing a greater proportional length and less flexion capacity. 

 The thigh and lower leg, on the other hand, are rather elephantine in their 

 shape and proportions, and indicate much less play at the knee-joint than in 

 the rhinoceros. The limb bones are relatively shorter than in Uintatherium, 

 but the metacarpals and tarsals are much longer and less spreading, thus 

 adding considerably to the height. These segments, combined with the elonga- 

 tion of the dorsal spines, gave Menodus as great a height as was attained by the 

 eocene genus, with its longer Hmbs. 



AMYNODONTID^. 



Ehinoceros-like animals, as far as yet known, extending from the Middle 

 and Upper Eocene (Bridger Beds) to the White River Miocene Beds ; horn- 

 less ; canines and incisors present in the typical number in both jaws ; pattern 

 of the premolar transitional to that of the molars ; first upper premolars rudi- 

 mentary or wanting; pattern of true molars like that of the rhinoceros, but 

 with the transverse crests simple; skull with a powerful sagittal crest. 



AMYNODON,* Mar.sh. 



Probable syn. Orthocynodon, Scott anrl O.sborn.t 



Dentition : I. f, C. \, Pm. |, M. |. Upper caninr:, obliquely placed; lower 

 canines erect and placed immediately in front r,f the upper when jaw is closed. 

 The third and fourth upper premolars only approacn the molar pattern by 

 the development of double transverse crests. First upper premolar small and 

 single fangec' . Post-glenoid and post-tympanic processes separate. 



* This Eocene genus, owing to the imperfect condition of the type skull in Pro- 

 fessor Marsh's coUectiou at the time of description, was incorrectly defined, (Am, 

 Journ. Sci. and Arts, 3d Ser., Vol. XIV. p. 251,) and the present writers, after a 

 personal examination, were led to believe that the type specimen of 0. antiquiis 

 represented a distinct genus. It now proves to be the same, as far as we know at 

 present. 



t E. M. Museum Bulletin, No. 3, May, 1883. 



