200 



BULLETIN 16 9, UNITED STATES NATIONAL MUSEUM 



Measurements of the three principal spedmens and statistical con- 

 stants of the whole series are given in tables 41 and 42 (see also fig. 4). 



Table 42. — Numerical data on lower dentition of Metachriacus punitor 



Three specimens from the Silberling Quarry, all very incomplete, 

 are referred to this species. Each is somewhat aberrant but not 

 consistently among the three and not beyond the established range of 

 variation. They are not included in the figures in table 42, which are 

 based on a pure sample from the Gidley Quarry. 



METACHRIACUS PROVOCATOR Simpson 



Figures 50-52 

 Metachriacus provocator Simpson, 1935d, p. 235. 



Type.— U.S. '^M. no. 9278, left lower jaw with P4-M3. Collected 

 by Dr. J. W. Gidley. 



Horizon and locality. — Type from Loc. 51, referred specimens from 

 Locs. 81, 50, 25, 24 (all below Gidley Quarry), Fort Union, Middle 

 Paleocene horizon. Crazy Mountain Field, Mont. 



Diagnosis. — Heel of P4 less expanded, httle or not basined, more 

 pointed posteriorly. Molars markedly crenulated. Mi_2 more 

 wedge-shaped, i. e., talonids markedly wider than trigonids. Slightly 

 but significantly larger than M. punitor in most dimensions (see 

 table 43). 



Discussion. — This species was originally based on three specimens 

 (Simpson, 1935d), but since then five more, less complete, have been 

 identified in the National Museum collection, and 10 have been col- 

 lected for the American Museum, so that it is now one of the best- 

 known species in the fauna. It does not occur in the quarries, where 

 it is replaced by the allied but certainly distinct M. punitor, but occurs 

 at the widely scattered Locs. 24, 25, 50, 51, and 81 (specimens from 

 25 and 81 only in the American Museum, but used in this study), all 

 of which are somewhat below the quarries, although all in Fort Union 

 No. 2. Both upper and lower jaws are known from each locality. It 

 is probable that the distribution, below the quarry levels, is accidental, 



