rOKT UXIOX OF CRAZY MOUisTAIX FIELD, MONT. 49 



absence in the Gidley Quarry is not due to time differences but to 

 facies or accidents of discovery. These species are Eucosmodon 

 sparsus,^'^ Mimotricentes angustidens, Didymictis haydenianus,^^ and 

 Tetraclaenodon symbolicus. Only two species, Psittacotherium multi- 

 fragum and Elpidophorus minor, known only from one specimen each, 

 are confined to the Silberling Quarry, and there can be no doubt that 

 this is the result of chance. The Gidley and Silberling Quarry 

 faunas are, then, a unit as far as appreciable differences in time are 

 concerned. 



The 575-foot level is represented by eight definitely identified 

 species, of which seven also occur in the Gidley or Silberling Quarries 

 or both, and the other, Metachriacus provocator, reappears at the 

 800-foot level. The 800-foot localities have 10 definitely identified 

 species, 8 of which also occur in the Gidley or Silberhng Quarries or 

 both, while Deuterogonodon monianus is confined to this level and 

 Metachriacus provocator appears also 225 feet lower. All the material 

 of Deuterogonodon monianus is from a single locality, and it must be 

 considered as a sporadic and chance occurrence with no probable 

 validity as an index of time relationship, particularly as no probable 

 or possible ancestral or descendent forms occur in this field. The 

 distribution of Metachriacus provocator is pecuhar. It is relatively 

 very abundant at No. 2 levels below^ the Gidley Quarry, being the 

 only species that occurs at all these locahties (except for Loc. 52, 

 which is only 50 feet below the Gidley Quarry and must be considered 

 as at essentially the same level) . At the Gidlej' and Silberling Quarry- 

 levels it has not been found, but an allied species, M. punitor, is 

 present and fairly commxon. M. provocator is the larger and in some 

 other respects probably the more speciaHzed of the two species, 

 despite its earUer appearance. Thus the relationship is not that of 

 ancestor to descendant, and no temporal difference is demonstrated. 

 The facies of these earlier locahties are demonstrably quite different 

 from those of the quarries, and the most reasonable conclusion is 

 that the distribution of the two species of Metachriacus is conditioned 

 by facies and not by time. 



It thus appears that the whole Fort Union No. 2 shows no probable 

 significant faunal advance and that it forms a unit as far as time and 

 correlation are concerned. 



It is particularly unfortunate that the three lower fossil zones of 

 the No. 3 beds are represented by few and poor specimens, for this 

 is a crucial point in the sequence, probably covering (as shown under 

 * 'Correlation") the transition from Middle to Upper Paleocene. The 

 lowest level, 1,350 feet, yields Claenodon fferox, Tetraclaenodon cf. 

 puercensis, and indeterminable pantolambdids. The latter have no 

 particular importance. Claenodon fjerox occurs almost throughout 



" These probably are present in unprepared Gidley Quarry material. 



