hay: on fossil \trtebrates. 43 



and-aft diameter of the crown is 16 mm.; the side-to-side diameter, 

 17.5. 



The outer styles are strongly developed, standing out boldly 

 from the face of the tooth. Near the grinding surface these styles 

 have a diameter of 2.5 mm., but toward the root the median widens 

 to 4 mm. The anterior one also widens slightly. 



The lakes have the enamel surrounding them only moderately 

 complicated. In the anterior lake there is a deep infold at the 

 hinder inner angle, and a smaller one in the hinder border. In the 

 hinder lake there are a shallow^ fold and another rather deep one 

 in the anterior border and a mxoderate one in the hinder border. 



The oval protocone is detached from the other columns of the 

 tooth, but lies close to them. A small loop at the head of the 

 hinder inner valley comes nearly into contact with the enamel of 

 the protocone. The inner face of the protocone is veiy slightly 

 convex. 



It is possible that the Hipparion teeth mentioned above as being 

 foimd in the Pleistocene of Missouri and Iowa belong to this spe- 

 cies; but while the crown of the Kansas specimen is veiy straight, 

 that of the ^Missouri tooth is considerably ciu'A'ed. The protocone 

 of the latter is considerably smaller than is the former. 



This tooth differs from those of H. gratinn, figured by Cope 

 iProc. Philos.Soc, vol. XXVI, figs. 16, 17) in being much straighter. 

 From these and most of those figured by Leidy (Jour. Phila. 

 Acad., vol. VII, 1869, pi. XVIII, figs. 25-30) the Kansas tooth 

 differs in ha\ing the enamel somewhat more simple in its arrange- 

 ment. 



Equus complicatus Leidy. 



In the Cragin collection there are a few teeth which are here 

 referred to this species. Of these there are one upper right pre- 

 molar and five lower cheek teeth. They were found on Spring 

 creek, near Meade. The upper premolar, the third or the fourth, 

 has a height of 80 mm., a length of 33 mm., and a width of 32 mm. 

 The protocone is 17 mm. wide. There is a deep reentrant loop at 

 the head of the postprotoconal valley, and the enamel of the lakes 

 is considerably complicated. 



Three of the lower teeth appear to have belonged to the same 

 animal. These are the two hinder premolars and the first molar 

 (pi. II, fig. 1). The following are the measurements: 



