NO. 2212. 



A NEW SPECIES OF EXTINCT HORSE— HAY. 



441 



the teeth push itself in between the longitudinally directed portions 

 of the valleys entering from the inner side of the tooth. On the inner 

 side of the tooth the groove between the metaconid and the metas- 

 tylid is very deep and it is angular at its inner end. The longitudinal 

 expansion of the hinder of the two inner valleys of the molars and 

 last premolar is directed obliquely to the long axis of the tooth. 



In the same mining claim, and apparently at the same depth, Mr. 

 Morrison found the right ramus of the lower jaw of another horse. 

 The ascending portion is missing. All the cheek teeth are present, 

 a large canine, and five of the incisors. The teeth show that the 

 animal was a male about 5 years old. The catalogue number in the 

 U. S. National Museum is 8427. 



That portion of the jaw which is preserved resembles consider- 

 ably that of E. lamhei in form and dimensions. It differs from the 

 latter and from all other equine jaws examined in having on the 

 outer face a strongly developed ridge, which, beginning at pm,, 

 runs downward and backward, reaching the lower border below 

 the penultimate molar. The thickness of the jaw at the last pre- 

 molar is 34 mm. 



The length of the premolar-molar series is 172 mm.; of the pre- 

 molar series, 90 mm. ; of the molar series, 83 mm. 



A comparison of these measurements and indices with those ob- 

 tained from the lower jaw of the type of E. lamhei shows that the 

 two sets of teeth agree in many respects. The differences might be 

 attributed to different stages of wear. It is not, however, certain 

 that the relations of length and width vary greatly with the stages 

 of wear in the lower teeth. 



When the structure of the teeth of the jaws of the two horses is 

 compared there appear various differences which seem to be im- 

 portant. The groove between the metaconid and the metastylid is 

 not so deep and angular in the odd jaw as it is in the type of E. 

 lamhei. In the third and fourth premolars of the odd jaw the longi- 

 tudinal portions of the anterior valley is broader and has a shallow 

 infolding of the enamel which does not appear in the other jaw. In 

 the molars the longitudinal portion of the hinder valley is not 



