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29 

 UINTA SELENODONTS 



ridge and surface are quite well marked and extend for a short distance upon 

 the maxillary. As a whole, the zygomatic arch is rather short, though rela- 

 tively somewhat longer than in Poebrotherium, decidedly slender and almost 

 straight, arching outward but little. 



The lachrymal is quite largely exposed upon the face in front of the 

 orbit, but its exact limits cannot well be determined, since only the suture 

 with the frontal is visible. 



The frontals are nearly as elongate in the antero-posterior dimension as 

 the parietals, though they take little part in roofing the cerebral chamber (as 

 is also the case in the modern Tylopoda) ; they are quite broad, the width 

 exceeding the length. The forehead is broad, smooth, lozenge-shaped, and 

 very slightly convex, both transversely and longitudinally. Anteriorly the 

 frontals are deeply notched to receive the nasals, but also send forward a 

 short, narrow tongue between the divergent ends of the latter ; the nasal pro- 

 cesses are short and blunt. Behind, the frontals give off a broad, triangular 

 process, which extends into the notch of the parietals already described. The 

 postorbital processes are quite long and distinct, but are shorter than in 

 Poebrotherium and much less decurved, leaving the orbit more widely open 

 behind. The orbit is also conspicuously smaller than in the White River 

 genus, and not nearly so deep, so that it is well separated from its fellow of 

 the opposite side, and not, as in Poebrotlierium, Leptomeryx, and the tragulines, 

 divided from it by a mere septum. The supraorbital canal opens much nearer 

 to the margin of the orbit than in Poebrotherium, in which it has shifted far- 

 ther towards the median line, and the groove which runs forward from the 

 foramen is much less deeply impressed than in the latter. The supraorbital 

 notch, which in the White River form is very deep, is much shallower in 

 Protylopus. A small vacuity appears to be formed between the frontal, nasal, 

 lachrymal, and maxillary. I speak thus hesitatingly, because the fontanelle is 

 not shown in Wortman's figure and because it may be due to distortion in the 

 Princeton specimens, though its shape is so symmetrical that such a mode ot 

 origin seems improbable. This opening is sometimes present in Poebrotherium. 



The nasals are very long and narrow; they are broadest just in advance 

 of the nasal processes of the frontals, narrowing both anteriorly and poster- 

 iorly from that point. The hinder ends diverge somewhat and receive 

 between them the short, narrow median processes of the frontals ; anteriorly 

 the nasals taper gradually to the free ends, which project somewhat beyond the 

 edges of the premaxillaries. In general, the nasals of Protylopus are much 



