372 THE rUEKCO FAUNA. 



Portions of a second individual of Mesonyx were found by Mr. Wort- 

 man in the Big Horn region. Of this I must observe that the head of the 

 radius has not the anterior flare of the inner side of the M. ossifragus, but it 

 resembles more nearly the corresponding part of the M. lanius, though it 

 presents some minor differences. The superior concavity is strong. The 

 axis vertebra has a rather long odontoid, with circular section and confluent 

 articular surfaces. The centrum has a strong hypapophysial heel, which is 

 laterally expanded posteriorly. The posterior articular face is moderately 

 oblique, and is plane excepting a central depression. The vertebrarterial 

 canal is wide. 



Comparison of this axis with those of Carnivora and Marsupialia yields 

 the following results: It differs from all the principal genera of the former 

 order, and from Didelphys and Phascolarctos of the latter, in the nearly 

 round form and downward extension of the atlantal facets. Tlie form is 

 approached by that of the Sarcophilus nrsinus, but is not so j)ronounced in 

 the latter. The strong hypapophysis is ai)proached by Felkhc only among 

 Carnivora, and by Dkhlphi/a among Marsupialia. The size of the axis is 

 about that of the Crocuta maculata. 



Two ungual phalanges which accompany this specimen have nuich the 

 form of those of M. lanius. The proximal part is claw-like, but the distal 

 part narrow hoof-like. The extremity is deeply fissured; the sides are 

 acute and flat, and there is a median inferior table, which widens poste- 

 riorly. It is separated by a groove from the lateral edge, which is deeply 

 impressed posteriori}-. Tlie acute lateral edges are spongy. 



Measurements of A'o. 2. m. 



Length of axia 1*0 



LeoRth of axis to base of odontoid ('48 



Diani.'t«T8 of atlantal facet| vertical (fji 



< horizontal VJl 



Width of centrum behind atlantal facet 032 



Diameters of posterior face centrum < " "'^ ,,„„ 



( tranHVeroe I'JO 



Diameters of head of radius^ "'"''=»' ^J^ 



I transverse y''^ 



Len)(th of phalange ' 



Diatoeters distal end phalange | ''•''■^''''' II*'l* 



( transverse •'!•' 



Length of nngnal phalange (•■-1 



Diameters proximally 5 ^"^""»1 ^"^ 



( transVctSe 010 



Width of expanse OlOS 



