Leidy, Proc. Ac. Nat. Sc., 1872, p. 169.--Cont. to Ext. Vert. Faun. of Western Territories, p. 93.--Cope, Hayden's Survey, 1872, p. 580, etc. Skull broader proportionally than in the other genera of the order, ridged and possessing several concavities on the upper surface; zygomas slender and but little curved; temporal fossæ comparatively short and have well-defined superciliary margins. The cervical vertebræ are rather long; the sacrum has four vertebræ; and the tail is quite long, very flat and broad. The tibia has its proximal face divided by a prominent ridge into two parts. The dental formula for the upper jaw is: I. 0, C. 1, M. 6. The molars are small, and increase from first to sixth. The last is much the largest; in it the anterior lobe considerably exceeds the posterior in size, and there may or may not be a tubercle at the entrance of the valley between the lobes; but there is always one developed from the cingulum at the posterior part of the tooth. Uintatherium leidianum, _sp. nov._[3] [Footnote 3: This species is respectfully dedicated to Dr. Joseph Leidy, of Philadelphia. The specimens upon which it is established were found on Dry Creek plateau.] Established upon a head and nearly perfect skeleton of one individual, and parts of two more. In this species, as in most others of the sub-order, the nasals are of immense length and thickness; they overhang the anterior nares, and project considerably beyond the premaxillaries; they form more than half of the entire length of the skull, articulating with the frontals somewhat behind the orbits; the median suture is distinct throughout. Instead of having an expanding shovel-shaped forward projection, as in _Loxolophodon_, they narrow from the median osseous projections (horn cores?) anteriorly. Above the muzzle they are strongly curved from side to side, on their upper surface forming a continuous arch; on the under surface of each bone is a deep concavity, separated from its fellow by the sutural ridge, which disappears forwards, near the extremity. On the upper surface of each nasal, near the forward end, is a large osseous tuberosity which is directed forwards and outwards; these processes are much smaller than the corresponding ones in the _Loxolophodon_, while they are larger, of different shape and direction from those in _Dinoceras_. In this species they are divided throughout by a deep median groove, which anteriorly becomes a fissure, and separates the extremities of the nasals completely. In front of these tuberosities, the nasals taper very rapidly, and end in sharp points which project downwards and forwards; this portion of the bones is shorter, sharper, and projects more decidedly downwards than in _Dinoceras_. Above and slightly behind the sockets of the cranium, the nasals and maxillaries give rise to the median pair of osseous projections. These are very large, subtrihedral at the base, and project upwards, outwards, and strongly forwards.