198 BULLETIN 16 9, Ui^iTED STATES NATIONAL MUSEUM 



Paratype.—V.S.^M. no. 9286, right lower jaw with P3-M3 (Mi and 

 M3 broken). Collected by A. C. Silberling. 



Type o/Chriacus pusillus.— U.S.N.M. no. 9270, right lower jaw with 

 P2-M2. Collected by Dr. J. W. Gidley. 



Horizon and locality.— Gidley and SilberHng Quarries, Fort Union, 

 Middle Paleocene horizon, Crazy Mountain Field, Mont. 



Figure il .—Mdachnacm punitor Simpson: a, L'.S.N.M, no. oa^S, left Mi_3 crown view; 6, U.S.N.M. no. 

 9286, with parts in outline from nos. 9282 and 9486, right lower jaw, external view. Twice natural size. 



Figure i&.—Meiachriacus punitor Simpson, small variation, U.S.N.M. no. 9270, right lower jaw, internal 



view. Twice natural size. 



Figure i'd.—Metachuacus punitor Simpson, U.S.N.M. no. 9331, left M'-', crown view. Four times natural 



size. 



Diagnosis. — Heel of P4 expanded, basined, squarely truncated pos- 

 teriorly. Molar crenulation moderate. Mi_2 less wedge-shaped. 

 Measurements given in tables 42 and 43. 



Discussion. — My earlier publication on the two species here united 

 was confused and incorrect. By a misinterpretation of a small worn 

 specimen and by the acceptance of an incorrect association, I was led 

 to place a few of these specimens in Chriacus and therefore I did not 



