OF THE WHITE RIVER BEDS OF MONTANA. 



275 



Oreodon. It is a lobe extending backward and upward and is broadly rounded at the 

 extremity, not forming a half crescent as in Diplopus. It has no raised border or ridge 

 projecting over the upper edge of the outer ridge of the proximal trochlea, as in the speci- 

 men No. 111G2 of the Princeton Collection, the foot of which is figured in Scott's paper 

 (1895, PL XXIV, Fig. 9). This articular surface occupies an elevated plane. The 

 posterior side of this elevation is higher than the anterior. 



The Tarsus. — The tuber of the calcaneum is most like that of Oreodon, but is much 

 more robust in proportion to its length, especially so at the upper extremity. It is like 

 that, too, in having no tuberosity or accessory facet on the sustentaculum, the inner 

 border of which is a sharp angle all around. 



The astragalus is longer in proportion to its width than in Agriochoerus, but much 

 shorter than in Hyopotamus or even Oreodon. In other respects it differs little from 

 that of Oreodon. The oblique ridge above the calcanear facet is not so prominent. As in 

 Oreodon, there is a faint ridge defining the inner boundary of the facet for the calcaneum, 

 but no massive ridge with an accessory facet as in Hyopotamus or Agriochoerus. 



The cuboid is much like that of Oreodon, but the calcanear notch is very shallow, 

 not descending so low as in that genus. In Hyopotamus it descends still lower. As seen 

 from the front the notch occupies only one-third the width of the cuboid, and it apparently 

 did not reach backward more than half the antero-posterior thickness of the bone. The 

 cuboid is more regular in outline and much nearer a cube than in Hyopotamus, Agrio- 

 chasrus and Oreodon. 



The navicular is more like that of Hyopotamus, but there is no plantar hook. 

 Behind the proximal articular surface there are two lobes, as a valley runs down the 

 plantar side. The inner lobe is the larger, projecting backward, so that, the inner length 

 of the bone is greater than that in Hyopotamus. The distal surface is nearly a plane 

 surface, with the exception of a small median inner convexity. The inner side is more 

 regular than in Hyopotamus. 



The ectocuneiform is nearly like that of Oreodon. There is a small facet for 

 metacarpal II, which has two faces, one more concave than the other. Above this is a 

 small triangular facet for tte mesocuueiform. On the plantar side there is a wide 

 groove or valley, passing obliquely downward and inward from the proximal to the distal 

 surface. 



The tarsus, as far as preserved, is characterized by its plainness and lack of compli- 

 cation. Unless the meso- and entocuneiforms were larger than common, there must have 

 been a large median plantar space unoccupied by tarsal bones. We have not the proximal 

 ends of the metacarpals, so it cannot be ascertained whether there were any posterior 

 prolongations filling this space or not. 



