30 Bulletin American Museum of Natural History. [Vol. XXXIV, 
molars and lack of a posterior crest of the protocone on upper molars. From 
Viverravus it is distinguished by the reduced premolars, short molars and 
retention of ms. It occupies therefore an intermediate position between 
these two genera. 
Uintacyon massetericus (Cope 1882). 
Didymictis massetericus Cope 1882, Proc. Am. Phil. Soc. Vol. XX, p. 160; 1885, 
fertiary Vertebrata, p. 312, pl. xxive, fig. 11; (Uintacyon) Matruew, 1909, U.S. 
G.S. Bull. 361, p. 93. 
Type, No. 4250, lower jaw with ps—mz |., from the Wasatch of the Big Horn Basin, 
probably Lysite or upper Gray Bull. 
Specific characters: pis = 17.5; mi_3 = 14. Heels of lower molars shorter and 
wider than U. jugulans, posterior accessory cusp of ps much smaller. 
Fig. 25. Fig. 26. 
Fig. 25. Uintacyon massetericus, upper jaw fragments with p+-m? left and p*—m! of right 
side, enlarged to two diameters, with outline of natural size. No. 157 19, lower Gray Bull 
beds, Big Horn Basin. 
Fig. 26. Uintacyon massetericus rudis. Type specimen, lower jaw fragment, natural 
size, outer view, and outer and crown views of teeth, twice natural size. Sand Coulée beds, 
Clark Fork Basin. 
In addition to the type I refer to this species two lower jaw fragments 
Nos. 15647 from the Lysite of the Big Horn Basin, No. 16749 from the 
upper Gray Bull beds, Big Horn Basin, and also No. 15719, upper jaw 
fragments from the Gray Bull horizon of the Big Horn. A nearly complete 
lower jaw, No. 16231, from the lower beds of the Wasatch of New Mexico 
also agrees quite closely with the type. 
