FORT UNION OF CRAZY MOUNTAIN FIELD, MONT. 



211 



Horizon and locality. — Gidley Quarry (one referred specimen from 

 Silberling Quarry), Fort Union, IVIiddle Paleocene horizon, Crazy 

 Mountain Field, Mont. 



Diagnosis. — Mucli smaller than D. haydenianus or any known later 

 species (see measurements below). P3 similar to P4, but cuspules 

 less well developed. P4 with large anterior cuspule, developed into 

 a small shearing blade, talonid relatively broad and less rounded than 

 in^other species, with one main cusp. M2 with shghtly elevated and 

 shearing trigonid, talonid reduced. 



Figure 5Q.—Did'jmictis microlestes Simpson, U.S.N.M. no. 9301, with parts in outline supplied from 

 U.S.N.M. nos. 6146 and 9306, left lower jaw: o, Crown view; 6, internal view. Three times natural size. 



FiGUEK 57.— Didymictis microlestes Simpson, U.S.N.M. no. 0299, with part in outline supplied from no. 

 6147, left P*-M', crown view. As preserved, P» is reversed (or rotated 180°) from the position shown 

 in the drawing, but this is believed to be accidental. Three times natural size. 



Discussion. — The morphological characters of this elegant little 

 species have been fully brought out in the comparison and diagnosis 

 above. The principal available numerical data on the lower dentition 

 are given in table 48. 



