TRANSACTIONS OF WAGNER 

 62 



UINTA SELENODONTS 



is somewhat shorter, a difference which is due to the position of the fibular 

 facet, and distinctly more slender, and the depression upon the external side, 

 while large and deep, is smaller and shallower than in the last-named genus. 

 The fibular facet is an elevated and regularly curved prominence, which is 

 placed somewhat more proximally than in Protylopus, thus making the tuber 

 shorter and the distal portion longer relatively. 



The cuboid shows no tendency to coossify with the navicular, and is 

 high and narrow, though distinctly less so than in Protylopus ; the astragalar 

 facet is very narrow and simply concave in the dorso-plantar direction ; it 

 rises high above the calcaneal facet in a very characteristic way, forming a 

 tall, narrow prominence, the internal (tibial) border of which is bevelled to 

 provide for the expansion of the navicular proximally. The calcaneal facet 

 is very deeply incised and its dorsal margin is far below that of the navicular 

 facet. This constitutes a very marked difference from the condition seen in 

 Protylopus, and is correlated with the relatively greater length of that part of 

 the calcaneum which lies distal to the fibular facet. The calcaneal facet differs 

 further from that of Protylopus in lacking the expansion upon the plantar side, 

 which in the latter forms an overhanging shelf. The plantar hook is narrow 

 and bluntly pointed, very different from the massive ridge which is found in 

 Protylopus. The distal end of the cuboid is mostly taken up by the large facet 

 for the fourth metatarsal, but posterior to this is a very small one for the fifth. 



The navicular is a large bone, exceeding the cuboid in every dimension 

 save the proximo-distal one; the proximal portion is expanded transversely at 

 the expense of the cuboid. The plantar hook is longer than in Protylopus ; but 

 more slender and pointed. The distal face is occupied almost entirely by the 

 facet for the compound cuneiform ; that for the internal one is very small and 

 placed at the postero-internal angle. 



The ento-cuneiform is small and flat and lies in the concavity embraced 

 by the plantar hook of the navicular; distally it bears a small, concave facet, 

 which suggests that at least a vestige of the first metatarsal was preserved. 



As in all the members of the present series from the Wasatch Trigono- 

 lestes (Pantolestcs) onward, the meso- and ecto-cuneiforms are firmly coossified, 

 but the shape of each element may still be distinguished. The meso-cunei- 

 form is very small and almost concealed when the pes is seen from the front, 

 while the ecto-cuneiform is very large and occupies nearly the entire breadth 

 of the navicular. This compound bone is quite like that of Protylopus, but is 

 shorter proximo-distally. 



