644 



TITANOTHERES OF ANCIENT WYOMING, DAKOTA, AND NEBRASKA 



of the Manteoceras-Dolichorhinus group rather than 

 of the palaeosyopine group. It does not belong to 

 the short-footed DolichorMnus Jiyognathus, but like 

 the foregoing (Am. Mus. 2352) may represent a long- 

 footed representative of this genus or of Mesatirhinus. 



Metarhinus? 



Provisionally referred pes from Uinta B 1. — To 

 Metarhinus are referred provisionally three hind feet 

 doubtfully recorded from the Metarhinus zone (Uinta 

 B 1), as follows: Am. Mus. 1950, a plaster cast from 

 a lost original; Am. Mus. 1947, including chiefly the 



Figure 572. — Pes referred to Mesatirhinus 

 Am. Mus. 2352; Washakie B (?) . One-third natural size. 



astragalus, calcaneum, and navicular; Am. Mus. 2058, 

 including among other fragments the astragalus and 

 metatarsals II and IV, from the top of horizon B. 

 These feet are referred to Metarhinus because no 

 skulls of Mesatirhinus but abundant skulls of Meta- 

 rhinus have been found at the geologic levels in which 

 they occur. 



The astragalus represents an advance upon the 

 Mesatirhinus type, from which it differs in the follow- 

 ing progressive characters: Trochlea a little more 

 flattened on the anterior face and a little wider in 

 proportion to the length (vertical diameter) of the 

 bone; process for ligament on posterosuperior border 



of internal face very pronounced; cuboid facet wider 

 (Am. Mus. 2058), sustentacular facet vertically 

 shorter and narrowing instead of broad superiorly, 

 ectal facet shallower. All these characters are seen 

 also in Dolichorhinus , in which, however, the astrag- 

 alus is larger, the sustentacular facet shorter and 



Figure 573. — Pes of Meta- 

 rhinus cf. M. earlei 



Am. Mus. 1950. Cast of left pes, partly 

 restored. One-third natural size. 



Figure 574. — Astragalus, cal- 

 caneum, and navicular of 

 Metarhinus cf. M. earlei 



Am. Mus. 1947. A, Front view of right 

 astragalus, calcaneum, and navicular; 

 B, distal view of astragalus and calca- 

 neum. One-half natural size. 



even more pointed above, and the cuboid facet wider. 

 The calcaneum (Am. Mus. 1947) has a long neck, 

 narrow sustentaculum, and in general resembles that 

 of Mesatirhinus, but the sus- 

 tentaculum is smaller and more 

 oblique and the top of the 

 prominence bearing the ectal 

 facet also shows a considerable 

 facet for the tibia; the ectal 

 facet itself is flatter; in most 

 points except size it resem- 

 bles the calcanea referred to 

 Dolichorhinus. 



The second metatarsal (Am. 

 Mus. 2058, 1950), closely resembles that of Mesati- 

 rhinus, and the same is true of the third (No. 

 1950) and the fourth (No. 2058). In the shape 

 of the facets they also resemble Dolichorhinus, but 

 they are distinguished by their slenderness. From 

 this close similarity in the pes to that of Mesati- 

 rhinus and also from the similarity in the dentition 

 and other parts we are led to expect that the 

 manus of Metarhinus will also be found to resemble 

 that of Mesatirhinus. 



Figure 575. — Astragalus 

 of Metarhinus cf. M. 

 earlei 

 Am. Mus. 1947. Rear view 

 (drawing from kft astragalus 

 reversed). One-third natural 

 size. 



