478 THE WASATCH FAUNA. 



M. 



Diameterof carpal facet I ^"•*'<=-''l ""^^ 



c transverse 008 



Length of radius 090 



Diameters of head of radius 5 "^^ertical 008 



< transverse 015 



Diameter at middle of shaft^ vertical. 006 



( transverse 009 



Diameters of distal enlargement^ ' 



< transverse 015 



T>- 4. J? 1 J- .( vertical (at lunar) 0075 



Diameters of carpal facet < 



( transverse Oil 



There is a similarity between Phenacodus and Hyrax in the proportions 

 of the ulna and radius. The carpal articulation of the ulna is, however, 

 quite different in the two. In Eyrax it is larger and more transverse, as in 

 Meplias. It is also larger in Hyrachyus. In fact, it is in Phenacodus much 

 like that of a carnivore. 



A part of the left anterior foot of this specimen is preserved. It is 

 smaller than the posterior foot, the metacarpals and phalanges having 

 smaller lengths and diameters. The thumb is as well developed as in the 

 P. primcevus, so that the presence of five toes in the manus is demonstrated. 

 But one bone of the carpus is preserved, the trapezoides. It differs consid- 

 erably in its form from that of the P. primcevus, having a nearly quadrate 

 anterior face, instead of a transverse one. It is considerably deeper antero- 

 posteriorly than wide, and has not the navicular-like shape of that of the 

 P. primcevus. On this account I compared it with the magnum, but in this 

 genus that bone has the usual posterosuperior convexity and posterior tu- 

 berosity. Both superior and inferior faces are concave anteroposteriorly. 

 The posterior extremity is narrowed, and is recurved obtusely above, in an 

 angle below. 



The head of the second metacarpal has the internal third defined as the 

 facet of the trapezium. The free edge of this facet overhangs a little the 

 first metacarpal in front, the latter fitting aa oblique groove of the second. 

 To the third metacarpal, the second presents a crescentic facet, which is 

 bounded below by a fossa. The shaft is not elongate, and the section is 

 oval, the edge next the pollex being thicker than that next the third meta- 

 carpal. Its distal extremity is about the size of that of the third, and larger 

 than that of the fourth. Its keel is distinct and exclusively posterior, and 

 is directed somewhat towards the tliird metacarpal. The first metacarpal is 



