212 BULLETIN 3 69, "UNITED STATES NATIONAL MUSEUM 



The type happens to be an unusually small specimen. It measures: 

 Length P4, 4.2; width P4, 2.1; length Mi, 4.3; width Mi, 3.2; length M2, 

 3.4; width M2, 2.2. 



Only two upper jaws and an isolated camassial are at hand, measure- 

 ments of which are given in table 49. 



Table 49. — Individual measurements {in mm) of upper dentition of Didymictis 



microlestes 



TlGVRE 68.— Didymictis tenuis Simpson, U.S.N.M. no. 9297, left lower jaw: a, Crown view; 6, internal view. 

 P4 is broken, and it may not be correctly placed. Six times natural size. 



DIDYMICTIS TENUIS Simpson 



Figure 58 

 Didymictis tenuis Simpson, 1935d, p. 238. 



Type. — U.S.N.M. no. 9297, part of left lower jaw with Mi and 

 broken 7?^. Collected by Dr. J. W. Gidley. 



Horizon and locality. — Gidley Quarry, Fort Union, Middle Paleocene 

 horizon. Crazy Mountain Field, Mont. 



Diagnosis. — Much smaller than any known comparable miacid. 

 Ml with very elevated trigonid, hypoconid and entoconid about 

 equally high and distinct. Mi length 2.9, width 1.8. 



