fa ' 



into. i. 



DESCRIPTIONS OF SOME NEW VERTEBRATA FROM THE 

 BRIDGER GROUP OF THE EOCENE. 



By E. D. Cope. 

 Mesonyx obtusidens. Cope. 

 Represented by a large part of .the skeleton of an individual of about 

 the size of the wolf {Ganis lupus). The lumbar vertebrae display the 

 short acuminate, and anteriorly directed cliapophyses, characteristic of 

 carnivora, while the astragalus resembles that of the same group. The 

 claws are flat and not curved. The molar teeth exhibit two principal 

 lobes and a thin rudimental at one extremity. The middle lobe is a com- 

 pressed cone, the posterior, a cutting edge, but medially placed, and less 

 acute than in Hyoenodoii, and the sectorial teeth of other carnivora, form- 

 ing a less specialized cutting apparatus. The canines are well developed. 

 A premolar is stout conic, with rudimental tubercle at base. 



M. 



Length of a sectorial (crown) 0.018 



Greatest width 008 



Elevation of crest 006 



Length of crown of a second 015 



Width 0065 



Elevation of middle lobe 014 



Length of crown of canine 026 



Diameter near base. . . , 014 



The number of the teeth cannot be determined, owing to the injured 

 condition of the jaw bones. The enamel is entirely smooth. 

 Found on the bluffs of Cottonwood Creek, Wyoming. 



Tkiacodon actjleatus. Cope. 

 Established on two teeth of the molar and premolar series. The molar 

 is subtriangular at the base of the crown, one side being convex ; the op- 

 posite angle nearly right, and the two remaining sides flat. The crown 

 is divided into three elevated trihedral cones, One at each angle. Their 

 adjacent angles are acute, and the angle of union is fissured, like the same 

 point in the sectorial tooth of a carnivora. The smaller lobes are of equal 

 elevation, but the crown of one is expanded so as to be slightly spade- 

 shaped. The enamel is smooth. 



M. 



Elevation of highest cusp 0.009 



" shorter " 007 



Long diameter base of crown 006 



" " " flat side 005 



The premolar is smaller, with shorter cusps, and one of the laterals re- 

 duced to a rudiment. 



This species is near the T. fallox of Marsh, but the tooth he describes 

 is narrower in proportion to its length, and has the anterior lobe little 

 over half as high. 



