M. Length of molar series ·148 Length of premolar series ·062 Length of true molar series ·089 Fore-and-aft diameter of second premolar ·022 Transverse diameter of second premolar ·023 Fore-and-aft diameter of third premolar ·022 Transverse diameter of third premolar ·023 Fore-and-aft diameter of first molar ·023 Transverse diameter of first molar ·026 Fore-and-aft diameter of second molar ·028 Transverse diameter of second molar ·031 Fore-and-aft diameter of third molar ·039 Transverse diameter of third molar ·044 Distance between last molars ·058 Distance between first premolars ·049 Distance between first molars ·074 Fore-and-aft diameter of root of canine ·060 Transverse diameter of root of canine ·039 Length of diastema ·072 Distance between canine alveoli ·080 _Lower Jaw._--Dr. Leidy has very kindly sent us some of the lower molars of an undescribed _Uintatherium_, which may belong to this species. They consist of the anterior lobe of the last molar, and second and third premolars entire. They all have nearly the same conformation, consisting of three acute pyramidal lobes, of which the anterior is very much the highest and broadest; the median lobe is partly separated from the anterior by a valley which opens outwards, while the valley between the posterior and median lobes passes completely across the tooth. The highest point of the crown is the inner end of the anterior lobe; but the difference between this and the outer end, very great in the molars, becomes slight in the premolars. The inner end has an accessory tubercle just at the lip of the anterior lobe, and there is another on the anterior basal ridge. This latter feature would seem to distinguish it from _U. robustum_. The basal ridge is distinct in front and behind, indistinct on the external side, and entirely absent from the internal. _Measurements._