FORT UXIOX OF CRAZY MOUNTAIN FIELD, MONT. 185 



such as are normally specific functions of size, but not in any essential 

 structure. 



As already suggested, Dr. Gidley's comparison with Ursus seems 

 to me to be beside the point and to involve no features not to be 

 expected by convergence in hea\aly built plantigrades not more closely 

 related than as members of wholly different groups of the same order. 



The species is surely distinct from C. Jerox, being excluded from 

 that group by the smaller size, reduced hypocone of M\ and reduced, 

 size and more transverse proportions of M^ (Some of the other 

 characters given by Gidley are not of probable specific value.) The 

 size is within the probable range of the small unnamed Torrejon 

 species. For instance, the length of M2 is 9.2 in the largest Torrejon 

 specimen of the small species and 9.4 in the type of C. montanensis. 

 The size distribution doubtless overlaps, but were a larger series 

 available it is probable that the mean for the Fort Union specimens 

 would be found to be significantly greater. The reduction of the 

 posterior part of M^ is also within the extreme limit of variabihty of 

 the Torrejon species but probably is a specific character varying about 

 a different, but not widely separate, mode. The somewhat smaller 

 hypocones of M^"^ and the less conical protocone of P* seem to be 

 beyond the lunits of the Torrejon specimens and thus still better 

 specific characters, on present data. Possibly correlated with the 

 differences in P^ is the somewhat narrower, more distinctly unicuspid 

 character of P4, also apparentlj^ a good specific character.^^ 



U.S.N.M. no. 9634 is an isolated Mi from the Gidley Quarry, 

 measuring 9.4 by 6.5 mm and referable to this species with Httle 

 doubt. No. 6159, from Loc. 52,^^ includes right and left Mg, appar- 

 ently associated, and other fragments, also referable to C. montanensis. 



CLAENODON SILBERLINGI (Gidley) 



Figure 40 

 Neodaenodon silberlingi Gidley, 1919, p. 552. 



Type.— U.S.N.M. no. 8363, part of left^" maxilla with P^-M^ and 

 alveoli for canine and P^"^. Collected by Dr. J. W. Gidley. 



Horizon and locality. — Gidley Quarry, Fort Union, Middle Paleo- 

 cene horizon, Sweetgrass County, Mont. 



Diagnosis. — Gidley (1919, p. 553): "A slightly smaller species than 

 N. montanensis from which it differs as follows: cusps of all the molars 

 seemingly^ more depressed; m^ and pm's^'* somewhat less reduced 



M These, of course, substantiate the validity of the still unpublished Torrejon species, rather than of C. 

 montanensis, which has priority and is surely distinct from any species previously named. 



83 Labeled '"Gidley Qu.' (Recorded Loc. 'No. 52' = Loc. No. 4)." Loc. 52 Is very near the Gidley Quarry 

 and about 50 feet lower stratigraphically. The difference does not appear to have any importance, but 

 the localities are not exactly the same. 



s* "Right" in the original designation of type (Gidley, 1919, p. 552) is a lapsus. 



"' Though found in its original bed, the enamel of all the teeth is considerably damaged through weather- 

 ing or leaching by surface water which had reached the specimen through cracks in the matrix." 



