56 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. I44 



an assortment of associated upper and lower teeth with jaw and other 

 fragments (U.S.N.M, No. 22461) from the earHer or Gray Bull 

 equivalent about 4 miles to the southwest of Elk Mountain in the 

 Fossil Basin may also represent this species. The upper teeth of this 

 specimen are noticeably larger than in either Sinopa multicuspis or 

 5. vulpecula, whereas the lower teeth compare very favorably with 

 the type oi S. strenua. 



MIACIDAE 



DIDYMICTIS PROTENUS (Cope) 



(Plate 7, figure 3) 



Among the materials that might logically be referred to earlier 

 Wasatchian Didymictis protenus is a lower jaw portion with P4 and 

 Ml (U.S.N.M. No. 22457) from the Bitter Creek locality. The size 

 of Ml appears to be close to that in Cope's type from New Mexico, 

 as measured at the roots, inasmuch as only the talonid portion of 

 this tooth is preserved in the type (U.S.N.M. No. 1092). P4, however, 

 is a little larger. Its principal cusp, moreover, is a little higher. Simp- 

 son (1937, p. 14) has noted considerable variation in size of materials 

 in the Gray Bull referred to D. protenus. 



This species seems also to be represented by tooth fragments from 

 the Gray Bull equivalent of the Knight west of Elk Mountain in 

 Fossil Basin. 



A remarkably good skeleton of Didymictis (P.U. No. 14917) from 

 about 15 miles north of Baggs, Wyo., is in the Princeton collection. 

 It is from the Knight beds just below the Tipton tongue, but is un- 

 usually small for this horizon. Measurements of the teeth are only 

 a trifle larger than in the type oi D. protenus to which it is very 

 tentatively referred. The possibility of its falling near the lower limit 

 of the range in size for the small mutant of £>. altidens should be 

 considered. Nevertheless, its size is well below the range noted for 

 the La Barge materials. The specimen is to be described in detail 

 elsewhere. 



DIDYMICTIS ALTIDENS Cope 



(Plate 7, figures i and 4) 



The reasons for referring the La Barge Didymictis materials to 

 D. altidens were discussed in 1952. The few specimens added to this 

 collection since that time furnish no further information. The 

 sample shows somewhat less variability than the Gray Bull materials, 



