63 



superciliary margins. The cervical vertebras are rather 

 long ; the sacrum has four vertebrse ; 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. o, C. i, 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. 



UlNTATHERIUM LEIDIANUM, Sp. 110V* 



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 pre- 

 maxillaries ; 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 pro- 

 jection, as in LoxolopJwdon, 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 sur- 

 face 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 LoxolopJwdon, 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 



* This species is respectfully dedicated to Dr. Joseph Leidy, of Philadelphia. 

 The specimens upon which it is established were found on Dry Creek plateau. 



