THE MAMMALIA OE THE DEEP KIVER BEDS. 177 



B. ANTELOPINUS. A. AMERICANA. 



M. M. 



Radius, length 198 .205 



Radius, breadth of proximal end 033 .036 



Radius, breadth of distal end 037 .033 



Radius, breadth of middle of shaft 024 .021 



Cannon-bone, length 181 .206 



Cannon-bone, breadth of proximal end 026 .027 



Cannon-bone, depth of proximal end 021 .019 



Cannon-bone, breadth of distal end 032 .026 



The femur is badly mutilated, having lost the articular portions of both extremi- 

 ties, and yet the part which remains is longer than the entire femur of Antilocapra ; 

 the shaft is arched forward, compressed and deep, and is decidedly heavier and of 

 less cylindrical shape than in the recent type. The distal portion is trihedral in sec- 

 tion and quite massive; the supracondylar fossa is more deeply marked and rugose 

 and the linea aspera is more prominent. 



The tibia is very similar to that of the prong-horn and of almost exactly the 

 same length, but heavier and of more massive construction throughout. The spine 

 is lower and less distinctly bifid, the cnemial crest heavier, more prominent and de- 

 scending lower upon the shaft. On the posterior face the roughened lines for mus- 

 cular attachment are much more prominent and rugose. The lower portion of the 

 shaft is less rounded, broader and more oval in section ; the distal end is broad and 

 heavy ; the fibular facet is altogether distal and shows that the fibula was reduced 

 to a mere nodule. The internal malleolus is very long, the posterior intercondylar 

 ridge or tongue is better developed than in the prong-horn, and the sulcus for the 

 flexor tendons is rather more deeply incised. 



The tarsus (PI. VI, Fig. 51) is completely modernized and may be briefly passed 

 over, as it presents but few characters of interest. The astragalus is both higher 

 and wider than in Antilocapra and in general outline is very similar to Fraas' figure 

 of Pakeomeryx furcatus (No. 16, PI. VIII, Fig. 13). The pit for the distal median 

 tongue of the tibia is much shallower than in the recent form and the facet for the 

 internal malleolus less deeply incised. The articular surface for the sustentaculum 

 is very large and passes without interruption into the distal trochlea ; the latter is 

 almost equally divided between the cuboid and navicular surfaces. 



The calcaneum is remarkably long, much more so than in the prong-buck or 

 Palaiomeryx furcatus ; this elongation, however, chiefly affects the tuber, the portion 

 distal to the sustentaculum being of nearly equal length in all three species. The 

 tuber is deeper (dorso-plantar diameter) and of more uniform depth than in Antilo- 



