1915.] Matthew and Granger, Lower Eocene Wasatch and Wind River Faunas. 19 
Didymictis Cope 1875.! 
Type, D. protenus (Copr 1874) from Wasatch of New Mexico. 
Syn., Viverravus Worrman (and Martrusw) 1899, MarrHew 1901, in part. 
Not Viverravus MarsuH 1872. 
Distinguished from Viverravus by the broader, basined heels of the lower molars; 
upper molars with metaconule and posterior crest of protocone well developed. 
This genus is among the most abundant and best known of the Lower 
Kocene Creodonts, ranging from Torrejon to Lost Cabin, the species pro- 
Fig. 12. Didymictis, upper teeth of D. altidens (Lost Cabin beds), D. protenus (Gray 
Bull beds) and D. haydenianus (Torrejon formation). All natural size, crown views. 
gressively larger and more robust, with the tubercular and sectorial denti- 
tion more clearly differentiated in the later species, the jaw heavier and 
deeper. 
The Torrejon Didymictis, D. haydenianus, differs materially from the 
later species, approaching Viverravus in the acute angulate form of the 
cusps, higher trigonid of me, and the compressed premolars, although it 
shows the basined heels of the molars which are the primary generic dis- 
tinction. 
1 Syst. Cat. Vert. Eoc. New Mex., p. 5. 
