12 



knowledge, the type of molar teeth in AncMppodus resembles that of 

 many ungulates, and it is not therefore probably allied to Synoplotherium. 

 Nevertheless it is far from certain that the teeth in question are incisors, 

 and that the genera are in nowise related, though a similar modification 

 of a remarkable character in distinct but co-existent types is by no 

 means an unprecedented circumstance. 



The remains on which the above identification is based, were found 

 by the writer on a terrace of the Mammoth Buttes near South Bitter 

 Creek in Wyoming. The cranium and fore foot and leg were excavated 

 from the deposit. 



Formation, the Bridger Group of the Eocene of Hayden. 



Prof. Marsh has described two genera of Carnivora from the same 

 formation, embracing species approaching this one in size. They are 

 both distinguished by the broader forms of the crowns of the inferior 

 molar teeth and other points. 



EXPLANATION OF PLATES. 



Plate I. Skull of SynoplotJierium lanius, .6 iiat. size ; tf, the tympanic 

 and opisthotic bones of the left side. 



Plate II. Fig. 1, End of muzzle of cranium of the same, from front : 

 fig. 2, the same from below. Fig. 3, metapodium, etc. of left fore foot. 

 Fig. 4, scaphoid bone of the same foot, a above ; 5 below. Fig. 5, Un- 

 gueal phalange separate. 



APRIL 19TH, 1873. 



