hay: on fossil vertebrates. 45 



The styles stand out prominently on the outer faces of the 

 teeth. As usual, the anterior one of the premolar is broader 

 than in the molars, but there is no defined groove running along 

 it. The protocone is slightly concave on its inner face. The 

 enamel of the worn teeth, especially that of the first molar, is 

 considerably complicated. There is a notch in the front wall of 

 the anterior lake, while in the hinder wall of the posterior lake 

 there is a deep infold and two or three shallow ones. The adjacent 

 borders of the two lakes have each a very deep infold and two 

 or three shallower ones. In the head of the postprotoconal valley 

 there is a rather deep reentrant loop. 



Besides the tooth described above there are seven loose upper 



premolars and molars, which were found along Spring creek, four 



miles southwest of Meade, Kan. I am not sure that the position 



of certain of the teeth has been correctly determined. In some 



cases, as Nos. 2 and 6 of the list below, the anterior style is narrow, 



indicating that the tooth is a molar, but it is traversed from end 



to end by a shallow groove. In another case, No. 1, the style is 



broad and without groove. The following are the measurements. 



It is to be understood that here, as in all other cases, the height 



of the tooth is given merely to show the amount of wear it has 



suffered. 



Measurements of teeth in millimeters. 



In the true molars of E. leidyi there appears to be a strong 

 tendency to retain the reentrant loop at the head of the post- 

 protoconal valley. 



Among the lower teeth of horses collected on Spring creek are 

 three premolars (pi. Ill, fig. 5) which appear to have belonged 

 in the left side of the same jaw; and three molars (pi. Ill, fig. 6) 

 which apparently belonged in the right side of the jaw of the 

 same individual as that which possessed the premolars, or of 

 another individual of the same age. The horses, if more than 

 one, were young, as will be seen from the height of the various 

 teeth. 



