LOXOLOPHODON AND UINTATHERIUM. 



19 



the Sub-order have already been pointed out, also the characters distinguishing 

 the genera known to the writer. In this memoir a careful description of 

 the skull of Loxolophodon Speirianum will be given, supplemented here and 

 there by details from Uintatherium Leidianum wherever the study of the former 

 is interrupted by imperfect preservation. The U. Leidianum skull will not be 

 here described in detail, as a careful description of it has already been given in 

 a former publication from this museum. This skull was found by Mr. Speir, a 

 member of the party of 1877. The basi-occipital and sphenoidal regions had 

 been exposed to the weather for some time, and were completely broken 

 away; in other respects it is perfect. As figured in Plate II., the outline of the 

 occiput is restored from the posterior half of another skull which we have 

 assigned to Uintatherium. The latter was procured two years later. It 

 happily fills the gap left in the occipital region of the U. Leidianu?n skull, 

 and admits of a close study of the bones and foramina of the two posterior 

 segments of the skull, including the periotic portion. It is regretted that we 

 have not as yet been able to obtain transverse sections of this specimen to 

 study the cavity of the brain and the petrous portion of the periotic. The 

 L. Speirianum skull, represented in Plate I., was obtained in the summer of 

 1878. It is wonderfully preserved, and has been put together with great skill 

 by the Curator of the Princeton museum. Unfortunately there is a wide break 

 at the base, between the palatines and the forward lower margin of the tem- 

 porals. The pterygoid bones, which form a deep backward continuation of the 

 posterior nares, are thus wanting in all our specimens. All the remaining bones 

 of the skull are represented in the different specimens. 



Comparison of the Skulls of Loxolophodon and Uintatherium. 



When placed beside each other, the skulls of the two genera offer a wide 

 contrast even under a rapid glance. Seen from above, the latter is one third 

 longer, while it is considerably narrower at the broadest point This chiefly 

 arises from the forward extension of the skull in front of the orbit, the distance 

 between the orbit and the occipital condyles being approximately the same 

 in both genera. The broadest portion of both skulls is between the parietal 

 and median protuberances. In Uintatherium the lateral expansion above the 

 orbits overhangs the zygomatic arches, while the Loxolophodon skull is gently 

 rounded at this point and the zygomatic arches project widely. The Uin- 

 tathcriiun nasals are shorter, and their processes are knobbed and project more 

 upwards. The fossa above the brain-case is deeper in Uintatherium. But by 

 far the most conspicuous feature of the skull is the huge size of both pairs 

 of protuberances — they are so out of proportion to the skull as to give it a most 



