Douglass : Ver tehkatks from Montana Tertiary. 



IGl 



covered with bony ossicles. They are higher and more conical than 

 in that genus, and instead of being marked with minute pits are cov- 

 ered with little rounded wart-like protuberances. The larger ossicles 

 ajjproach a pentagonal or hexagonal form at the base. Two, near the 

 middle of the head, are elongated transversely. Anterior to these 

 there is no bilateral symmetry in their arrangement or size. The 

 posterior ones, as in Hcjodcrma, are smaller than the anterior 

 ones. 



The mandible shows three foramina on the outer surface. The 

 teeth, which are partly set in the jaw, are sharp, laterally compressed 

 near the apex, and incline slightly backward. 



Length of fragment of skull, 40 mm. 



r> '^^ 



M.\MMALIA. 



.pI':rissodactyta. 



Mesohippus latidens sp. nov. 

 No. 751. Fig. 7. 



The type of this species is a portion of a crushed and flattened 

 skull with the last premolar and the molars of both sides. It was 

 found in the Lower White River beds near Three Forks in 1899. 



The most striking distinguishing 

 character of the teeth is the ex- 

 treme transverse as compared with 

 the antero-posterior diameter and 

 the much greater width of the an- 

 terior than of the posterior por- 

 tions. The teeth are more prim- 

 itive than those* of J/, bairdi. The 

 median tubercles of the anterior 

 cross-crests are much larger than 

 those of the posterior cross- crests. 



The posterior intermediate cingular cusps are represented by only 

 a minute enlargement or thickening of the cingulum. There are 

 no cingula on the inner faces of the inner cusps except on M^. 

 There are faint median ridges on the outer crescents. The posterior 

 intermediate cusps on the cross-crests decrease in size from Mi 

 backward. On M^ this cusp can hardly be distinguished from the 

 cross-crests. 



Fig. 7. ■ Mesohippus latidens (No. 

 751). Last upper premolar and the 

 three molars of left side. Natural 

 size. White River beds near Three 

 Forks. 



