514 THE MAJNIMALIA OF THE UINTA FORMATION. 



It is not possible to determine tlie species to wliieh our skeletal remains of Dip- 

 lacodon belong, as we have but a portion of a single upper molar. They may be 

 referred to D. elaius. Palceosyops has hitherto been referred to the Chalicotherudce, 

 but the discovery of the foot bones of Chalicotherium by Filhol shows that the genera 

 are Avidely separated. The discovery of the skeleton of Diplacodon, however, links 

 Palmosyops very closely to Titanotherium, and the differences between these three 

 genera are principally in three characters, viz., the assumption of the molar pattern 

 by the premolars, the development of frontal horns, and the loss of the incisor teeth. 

 If these charactei's are given a family I'ank we cannot decide where to place Dipltico- 

 don. It seems best to group the three genera in the single family TitanotJieriidce.* 



DiPLACODON ELATUS. 



Generic characters. Dentition, fourth and third upper premolars like the 

 molars. Last upper molar with single internal cone. Digits 4-3. 



8p(cijiG characters. Second upper premolar with a rudimentary postero-internal 

 cusp, like the molars. 



As above stated, the specific reference of these specimens is uncertain. The cer- 

 vical vertebras are much shorter than those associated with the Yale College speci- 

 mens. It is probable that they represent a distinct species. 



The Skeleton. 



Plate VIU. 



Cervicals. The axis (Xo. 10,396a), Fig. 15, has a broad spine overhanging 

 the postzygapophysis. The laminae are very slightly notched. The postzygapophy- 

 ses are an elongate oval. The transverse processes are hooked, turning inwards at 

 the tip and perforated at the base. The centrum presents a sharp inferior keel. The 

 remaining cervical'^ and dorsals belong to a single individual (N^o. 10,39(5). The 

 cervicals preserved are probably the 3d, 4th, 5th and Gth. The 5th is the most com- 

 plete (Fig. 1) ; the spine is pointed, vertically placed and grooved posterioi'ly ; the 

 zygapophyses are very stout with the facets placed at angles of -15° ; the vertical 

 diameter of the centra is much gi-eater than the transverse; they are quite strongly 

 opisthocoilous 3 the transverse processes do not extend below the level of the 

 centrum. 



The centra of seven dorsals arc preserved. The one figured is between the 



* Tliis generic luid lamily iiiiiuu has lici'ii ailoplcil liy llu; writcT because Menodiis Pomul is louiul to be pruoccupied 

 by Jlenodon v. Meyer, and Tiliinothcriiini Leidy niiisl supersede i(. 



