TRANSACTIONS OF WAGNER 

 9° 



UINTA SELENODONTS 



The skull (Plate III., fig. 19; Plate IV., fig, 24) is represented by several 

 fine specimens in the two collections, which give a much more accurate idea 

 of its structure and proportions than did the single very imperfect individual 

 upon which my previous description was founded. ('89, pp. 488-490.) It is 

 now obvious that the whole appearance and character of the skull are typically 

 oreodont, though certain resemblances to the agriochcerids may be made out, 

 and in several respects the skull, as would naturally be expected, is decidedly 

 more primitive than in the White River representatives of either family. The 

 cranium is long and narrow and low, especially in P. paradoxicus, and the face 

 is short; the position of the orbit is somewhat variable, its anterior border 

 being over the front part of vcfi- or the hinder part of ml. The occiput is 

 low and narrow, and is drawn out dorsally into the wing-like processes so 

 characteristic of the family; the zygomatic arch is slender, elongate, and 

 nearly straight, and the orbit is widely open behind. No lachrymal pit has 

 been detected. The muzzle is short, but narrow and tapering and abruptly 

 truncate in front. The mandible is characteristically oreodont in form. 



In details the skull structure is completely oreodont, though in several 

 respects it is more primitive than that found in the genera of the White River 

 and succeeding stages. The basioccipital resembles that of Oreodon, but is 

 somewhat narrower, as are also the exoccipitals, but the foramen magnum is 

 relatively much larger and the condyles more widely separated. The par- 

 occipital processes are slender and appear to be relatively less elongate than in 

 the White River forms ; they have a rather more anterior position than in the 

 latter. The limits of the supraoccipital are not clearly shown in any of the 

 specimens, though doubtless it extends over upon the dorsal side of the 

 cranium as it does in Oreodon, and, as in that genus, it forms a pair of promi- 

 nent wing-like processes which extend backward, overhanging the occiput ; 

 they are best developed in P. paradoxicus, in which they are quite as conspicu- 

 ous as in 0. culbcrtsoni. The occipital crest is not very prominently developed 

 and does not pass so directly into the root of the zygomatic process as it does 

 in the later genera of the family. In none of the individuals that I have ex- 

 amined is the tympanic well preserved ; it is almost certain, however, that the 

 bulla was very small and that it was provided with a tubular meatus, much as 

 in 0. culbcrtsoni. 



As in the White River genus, the parietals are very long, roofing in 

 nearly the whole of the cerebral fossa, and they ar.e somewhat broader pro- 

 portionately than in the former. For their entire length they support a thin 



