DAKOTA AND NEBRASKA. 



317 



half worn away. The teeth are larger in their proportions than in the preceding 

 specimens, and would appear to be even simpler in their constitution at the same 

 stage of abrasion, as represented in the view of the triturating surfaces in figure 18, 

 plate XIX. 



The measurements of the teeth are as follow : 



Lines. 



. 7 



Length of crown at fore part externally of fifth molar, 

 Breadth of fifth molar, .... 



Length of crown at fore part externally of last molar, 

 Breadth of sixth molar, .... 



9 



7 



13 



4. Three symphysial portions of as many jaws, having the same general form as 

 the corresponding part in the Ass. They belonged to animals of nearly the same 

 size, but vary among one another in their relative proportions. One contains the 

 fangs of all the incisors and canines. The latter appear to have been of robust 

 character, and they formed a continuous semi-circle with the former. The other two 

 specimens, slightly less constricted and flatter below than in the preceding, were de- 

 void of canines. 



5. A number of isolated incisors and several canines, resembling in constitution 

 those of living equine animals. 



6. A series of lower molars of the right side, except the first one. They are well 

 preserved, and less than half worn. Though isolated and mingled with a multitude 

 of other specimens, they are supposed to belong together from their agreement in all 

 essential characters. Their triturating surfaces, with the addition of that of a speci- 

 men of a first molar from another animal, probably of the same species, is represented 

 in figure 3. This series of molars I suspect to belong to one of the species of Hippa- 

 rion, — probably H. affine, or perhaps H. occidentale. 



The measurements of the teeth are as follow : 



Lines. 



68 



