36 



E. L. Troxell — Horned Eocene Ungulates. 



The protoloph, the anterior cross ridge, on P 34 is 

 patterned after the molars; but the metaloph is 

 extremely small and irregular. It consists of a small 

 tubercle situated between two folds of enamel extending 

 inward from the proto- and tritocones, and is distinctly 

 separated at the ends from both the ecto- and protolophs 



From the drawings it may be seen that the main 

 valleys of the premolars open backward instead of inward 

 and in this respect are like those of Ccenopus platy- 

 cephalus nanolophus. 



10258 TYPE 

 Y. P. M. 



Fig. 5. — Metahyrachyus bicornutus, gen. et sp. nov. Crown view of upper 

 teeth and part of skull. The diastema between the canine and molar is 

 reduced to half its normal length of 25 mm. by the distortion of the skull. 

 The chief distinguishing features are found in the unusual premolars. X%- 



Of the teeth of the cheek series the second molar is 

 largest ; it approaches in size that of Hyrachyus princeps 

 Marsh. The third molar is relatively small and its outer 

 and posterior sides form a fairly smooth curve, with the 

 ectoloph extending slightly beyond its edge. On this 

 third molar the posterior cingulum is conspicuous ; a 

 small overlapping cingulum across the median valley 

 corresponds to the small cusp which lies on the base of the 

 protocone of M 2 . 



The inner side of the ectoloph of M 3 is nearly straight 

 in this specimen. Back of the point of union of the 

 metaloph, only, does it curve outward and away from the 

 straight line, where it forms a thin, prominent edge. The 

 small crista is far back on the paracone and lies low on 

 its base. On M 1 it is higher and farther forward. 



On all the molars, the parastyle, antero-exterior corner, 

 is rather small and is not set off from the adjacent proto- 

 loph by such sharp grooves as one sees in Hyrachyus 

 princeps. 



