Douglass : Fossil Horses. 273 



verse diameter at its narrowest part is one-twentieth its length. The 

 tibia is nearly a fourth longer than the radius. Its length is fourteen 

 times its narrowest transverse diameter. The shaft of the outer lateral 

 metatarsal is considerably more reduced than that of the inner meta- 

 tarsal. The lateral phalanges are considerably shorter than the median 

 phalanges, therefore the tips of the unguals were evidently free from 

 the ground when the animal was standing. The lateral unguals, like 

 the median, are slender. 



A remarkable characteristic of this horse is the extreme length and 

 slenderness of the limbs combined with the primitive pattern of the 

 teeth, which, with the exception of the somewhat greater height of the 

 different elements and the partial separation of the metaconid and 

 metastylid, are scarcely more progressive in the direction of the mod- 

 ern horse than are the teeth of some of the horses of the Lower Oli- 

 gocene ; though apparently the horse here described is not older than 



Middle Miocene. 



Measurements. 



mm. 



Length of Upper Molar-premolar series except M-3- 88 



Length of Upper Premolar series 58 



Length of Mi 15 



Width of Mi 18 



Height of Mi 13 



Length of M^ 15 



Width ofMi 18 



Length of first lower temporary molar 6.5 



Width of first lower temporary molar 4 



Length of second lower temporary molar 18 



Length of third lower temporary molar 16 



Length of fourth lower temporary molar 15.5 



Length of M T 15 



Width of Mj 10 



Height of M T 13 



Length of radius 173 



Width of shaft of radius, least 14.5 



Length of tibia 225 



Width of shaft of tibia, least 16 



Length of median metatarsal, not less than 167 



Length of median metatarsal, estimated 180 



Width of shaft of median metatarsal 12.5 



Length of median ungual phalanx.. 28 



Width of median ungual phalanx 19 



Length of lateral ungual phalanx 19 



Width of lateral ungual phalanx 7 



