nr WALCOTR 



A V P END IX. 



Aim-. LIX. — Notice of New Tertia/ry Mammals; by 



('). C. Marsh. 



Recent researches in the Tertiary deposits of the West have 

 made known several new forms of large mammals, some of 

 which are here briefly described. All the latter are from the 

 Brontotherium beds of Dakota, and show a closer connection 

 of the fauna of these deposits with that below than has hitherto 

 been suspected. They will all be described more fully by the 

 writer in a later communication. 



Dlploclotixis ampins, gen. et sp. nov. 



The type-specimen of this genus is a nearly complete skull, in 

 good preservation, but without the lower jaws. One of the most 

 marked features is seen in the horn-cores, which are high, com- 

 pressed transversely, and have a prominent knob on the inner 

 superior margin, about one-third of the distance to the sum- 

 mit. Seen from the front, the horn-cores thus appear to be 

 branched. It is probable that in life this feature was still 

 more evident, and the covering of the horn-core may have 

 shown an actual division, but this cannot he determined from 

 the present specimen. There is a sharp ridge at the base of 

 the horn-cores on the outside. 



The nasals project but very little in front of the horn-cores. 

 The zygomatic arches are especially strong, and widely ex- 

 panded. The posterior nares have their front margin opposite 

 the back of the last upper molars. 



There were apparently bnt two upper incisors, and no dias- 

 tema exists behind the canines. The premolars have a strong 

 inner basal ridge, and the last upper molar has two inner cones. 



This genus appears to be most nearly related to Titanops, 

 but the norn-cores will distinguish it readily from all known 

 forms of the Brontothefidm* 



33a 



