252 EOCENE FAITN.-E. 



belong to the same greater division. In the same way Miaci^ must probably 

 follow Didymictis. For the present, then, I refer the genera of the Bridger 

 formation known to me, tu thu Creodonta. 



The affinities of the Creodonta may be estimated as follows : 



The glenoid cavity of the squamosal bone is transverse, and well defined 

 anteriorly and posteriorly, as in the Carnivora. In all the genera of the 

 Suessonian or Wasatch, the ilium has a well-marked external anterior ridge, 

 which continues from the acetabulum to the crest, distinct from the internal 

 anterior ridge. The ilium has therefore an angulate or convex external 

 face, as in Insedivora and Marsupialia, and does not" display the usual 

 expansion in a single plane of most of the placentals. In all the genera 

 there is a strong tuberosity in the position of the anterior inferior spine, 

 which is wanting in the Mammalia, excepting certain Imedivora and 

 Prosimice, although it marks the position of the origin of the rectus femoris 

 muscle in all types. 



In Amhlydonus, Didymictis, Protopsalis, and three undetermined forms, 

 the femur supports a third trochanter. 



In some species, where the cuboid bones are preserved, it is evident that 

 the distal end of the astragalus articulated with this as well as with the 

 navicular bone, although the facet of the astragalus is single and continuous. 

 As the extensive transverse distal astragalar face is characteristic of all the 

 species where it is preserved, the contact of the cuboid and astragalus is 

 probably common to all of this division. There is no elongation of the 

 navicular ; it is, on the contrary, very short, since the astragalus projects 

 beyond the calcaneum (in the genera where they have been observed). The 

 cuboid is, on this account, rather elongate, but not remarkably so. There 

 were five toes in the hind feet of some of the species. The ungues in some 

 of the genera are compressed and acute. In the genus Mesonyx, from the 

 Bridger, I found one of the claws to be broad and flat, so as to be subun- 

 gulate I found an ungual phalange in New Mexico, probably belonging 

 to a species of this group, which |)resented a simihu-, though less expanded, 

 form. I have every reason t'nr believing that there were five toes on the 

 hind foot f)f Stypolophus hians and a second species. 



