FOKT UNION OF CRAZY MOUNTAIN FIELD, MONT. 



255 



External cingulum absent, talonids incipiently lophoid. Talonid of 

 M2 markedly narrower than trigonid. Lower molars of about the size 

 of those of Tetraclaenodon symhoUcus but slightly narrower relatively. 

 Somewhat longer and distinctly wider than those of 1G. silberlingi. 

 M2 length 7.7, trigonid width 6.2, talonid width 5.5. 



Figure 7i.—'!Gidteyina superior (Simpson), U.S.N.M. uo. iiyid, leu lower jaw: o, Crown view; 6, internal 

 view. One and one-balf times natural size. 



Remarks. — This distinctive but imperfectly known species was at 

 first referred, with a query, to Tetraclaenodon, but with the comment 

 that it might belong to Gidleyina. The crucial evidence of the pre- 

 molars is lacking, but after further study it seems probable that it is 

 congeneric with IGidleyina silberlingi. The relatively slight enamel 

 crenulation, the structure of the trigonids, and the incipiently lophio- 

 dont talonids are distinctions from species surely referred to Tetra- 

 claenodon and points of resemblance to ?6^. silberlingi. Reference to 

 Gidleyina depends on that of the last-named species, discussed above. 



Family PERIPTYCHIDAE Cope, 1882 

 Subfamily Anisonchinae Osbom and Earle, 1895 



Anisonchines are among the commonest fossils in the Puerco and 

 Torrejon, but in the present fauna they are neither abundant nor 

 varied. One form cannot at present be distinguished from the 

 Torrejon species Anisonchus sedorius. Only one other form, Cori- 

 phagus montanus, is recognized. This genus also occurs in the Torre- 

 jon, but the species is distinct. The recognition that Mixoclaenus 

 is a synonym of Coriphagus and that these animals are not oxy- 

 claenids, as generally supposed, but primitive anisonchines clears up a 

 decided taxonomic anomaly and also casts important light on the 

 origin and affinities of the Anisonchinae. 



The five genera of tliis subfamily so far distinguished may be recog- 

 nized by criteria presented in table 59. 



