Peterson : A New Titanothere from the Uinta Eocene. 49 



Fig. 14. Diplocera 

 osborni Peterson. (Pa- 

 ratype. No. 2860.) X 3. 

 Posterior view of astra- 



the present form is seen to be as long in proportion and compressed 

 laterally to the same extent, while that portion carrying the susten- 

 tacular facets is longer. The fibula also appa- 

 rently articulates with the calcaneum, but the 

 posterior portion of the tibial trochlea did not 

 touch the calcaneum as in Diplacodon and 

 Titannthcriiim. The astragalus is higher and 

 narrower, and the metatarsals are longer and 

 much slenderer than in the latter genera. 



When compared in more detail there are a 

 number of dififerences between the genera here 

 compared. On the calcaneum of the genus un- 

 der description the proximal astragalar facet „^i 

 is not raised as high above the surface as in 



Titanotherinm. The greater process of the distal end extends lower 

 down and the facet for the cuboid is more oblique than in Titano- 

 therinm. As already stated, the astragalus is 

 higher and narrower, the trochlear groove is 

 deeper with the articular surfaces of the two 

 condyles steeper, and the neck separating the 

 distal end from the trochlea longer than in the 

 astragalus of the Oligocene form, and also some- 

 what longer than in Diplacodon as figured by 

 Scott and Osborn. Furthermore, the distal 

 end of the astragalus of the present form is 

 more unequally divided by the navicular and 

 cuboid facets than in the Oligocene genus. 

 These facets of the astragalus in Titanotherium 

 are more nearly subequal in size, the cuboid 

 facet having increased in size, as well as being 

 located more distally on the bone, while in 

 Diploceras this facet occupies a comparatively 

 narrow area on the fibular angle and is placed 

 laterally. 

 The most noticeable difference of the astragalus of Diploceras 

 osborni and that of the Princeton specimen as figured (/. c, PI. VIII, 

 Fig. 8&) seems to be in the three distinct astragalar facets (viz. ectal, 

 sustentacular, and cuboidal) of the latter, while in the present form 

 the ectal, besides extending higher, unites with the cuboidal facet 



Fig. 15. Diploceras 

 osborni Peterson. (Para- 

 type. No. 2860.) X i. 

 Dorsal view of pes. 



