UPPER JAW. M. Length of entire dental series ·275 Length of incisor series ·375 Length of diastema between canine and incisors ·018 Fore-and-aft diameter of canine ·019 Transverse diameter of canine ·015 Length of diastema between canine and premolars ·0145 Length of premolar series ·083 Length of first premolar ·016 Width of first premolar ·009 Length of second premolar ·021 Width of second premolar ·017 Length of third premolar ·022 Width of third premolar ·022 Length of fourth premolar ·024 Width of fourth premolar ·027 Length of true molar series ·106 Length of first molar ·031 Width of first molar ·031 Length of second molar ·037 Width of second molar ·040 Length of third molar ·038 Width of third molar ·041 LOWER JAW. M. Length of entire molar series ·202 Length of premolar series ·081 Length of true molar series ·121 Length of second premolar ·024 Width of second premolar ·0125 Length of third premolar ·022 Width of third premolar ·014 Length of fourth premolar ·0235 Width of fourth premolar ·0155 Length of first molar ·030 Width of first molar ·017 Length of second molar ·038 Width of second molar ·021 Length of third molar ·053 Width of third molar ·024 Found at Henry's Fork Divide. This may eventually prove to be a species of _Telmatherium_, (Marsh); but the description given by him of that genus is so brief and uncharacteristic that it might apply to any of the allied genera. Indeed, Dr. Leidy has regarded it as a synonym of _Palæosyops_. HYRACHYUS, Leidy. Proc. Ac. Nat. Sc., 1871, p. 229, _et seq_. A genus of tapiroid mammals, which is thus defined: "_Lower Jaw:_ Third molar with two crests; four premolars, third and fourth with one transverse and one longitudinal crest. _Upper Jaw:_ Seven molars, first without interior heel; premolars with two transverse crests." (Cope.)