PROTHEOSODON CONIFERUS 47 



from the ectal. On the external side the astragulus carries 

 an expanded articular facet for the inner side of the fibula, 

 which, instead of being vertical, is expanded below, mak- 

 ing an oblique face which is continuous with the fibular 

 facet on the calcaneum. In this feature Prothcosodon is, 

 as far as the feet are known, unique. 



The calcaneum is a long bone with a club-shaped expan- 

 sion of the upper end. The fibular facet is small, being 

 continuous, as above described, with that on the outer 

 side of the astragulus. On the face toward the astragulus, 

 the ectal facet is broadly convex (not divided as in Thco- 

 sodon), while the sustentacular facet is slightly concave. 

 The distal end is occupied by the large concave facet for 

 the cuboid. 



The navicular is of moderate height, with a prominent 

 hook behind. On the upper surface is only the broad, 

 deep facet for the astragulus; while the lower surface is 

 divided into facets for the tnree cuneiforms, and the ex- 

 ternal distal margin is beveled to make a narrow facet for 

 the cuboid. This navicular differs from that of Theosodon 

 in that the facet for the ectocuneiform is not cut step-like 

 into its external face. 



The endocuneiform is a small scale-like bone with a 

 narrow facet on the navicular, and overlapping the inner 

 side of Mt. II. The mesocuneiform is small, with a flat 

 facet above for the navicular, and a convex one below for 

 Mt. II. which is carried wholly on this bone. The ecto- 

 cuneiform is far the largest of these three bones, and car- 

 ries a broad facet above for the navicular, a similar one 

 l>elow for Mt. Ill, a small facet on the internal side for the 

 mesocuneiform and a second one below that for the side 

 of Mt. II, while externally there are facets for the cuboid 

 and for the side of Mt. IV. 



The cuboid is large, the external side being longer than 

 the internal. The upper surface is entirely occupied by 

 the facet for the calcaneum, while the lower face is mostly 

 devoted to the facet for Mt. IV, with a narrow streak on the 



