FORT UNION OF CRAZY MOUNTAIN FIELD, MONT. 



201 



that is, that M. provocator is not a significantly older species replaced in 

 time by M. punitor, but that they may well have been really contem- 

 poraneous but living in different facies. 



In addition to the characters cited in the diagnosis, the two speci 

 mens of M. provocator that show the alveoli of Pj had this tooth 

 relatively more reduced than in M. punitor, with more definite diaste- 

 mata before and behind it. 



The upper molars, well known in this species, have the hypocones 

 more definite and more projecting internally than in M. punitor, and 

 M^ is less reduced and less transverse. There is also a tendency to 

 develop a rudimentary protostyle on M^. These characters make the 

 upper teeth closer to Chriacus than are those of M. punitor, and the 

 upper dentition of M. provocator would not perhaps in itself be sepa- 

 rated generically from Chriacus, but its lower dentition shows the 

 generic characters even more clearly than does that of M. punitor. 



There are three lower and three upper jaws, some associated, from 

 each of Locs. 25 and 51, three lower and one upper from Loc. 81, two 

 lower and one upper from Loc. 50, and one lower and one upper from 

 Loc. 24. Deviations exist, of course, between the material from dif- 

 ferent localities, but these are not consistent and are not statistically 

 significant. The samples are too small to demonstrate racial dif- 

 ferences, if such exist. In fact the whole combined sample does not 

 exceed the variety usual in a homogeneous species but on the con- 

 trary shows unusually small variation, as shown by the figures in 

 table 43 (see also fig. 4). 



Table 43. — Numerical data on upper and lower dentition of Metachriacus 



provocator 



In only one case does the coefficient of variation exceed 5 (this 

 would be true also if this coefficient were calculated for all the variates) . 



