56.9¢(1181:78.7) 
Article X.— A REVISION OF THE LOWER EOCENE WASATCH 
AND WIND RIVER FAUNAS. 
By W. D. Matruew anp WALTER GRANGER. 
PART III.— GRDER CONDYLARTHRA. ° 
FAMILIES PHENACODONTIDAL AND MENISCOTHERITDA. 
By WALTER GRANGER. 
Family PHENACODONTIDE Cope, 1881. 
Four genera have been commonly placed in this family, Protogonodon 
and T'etraclenodon from the Puerco and Torrejon formations, respectively, 
of the Basal Eocene, and: Phenacodus and Ectocion from the various horizons 
of the Lower Eocene. Of the genus Protogonodon from the Puerco the writer 
feels that it should be removed from the family, the chief reasons being the 
lack of anything like a well developed hypocone on the upper molars and 
the basining of the lower molars. Earl has suggested ' its affinities with the 
ancestral Artiodactyl stem and while the lower molars do resemble very 
much those of the Bunodont Artiodactyla of the Lower Eocene, yet the 
premolars are already showing a tendency toward complication as evidenced. 
by the presence of an incipient metaconid on py. It seems more probable 
that Protogonodon is a Creodont belonging to either the Oxycleenidee or 
Arctocyonidee. 
If Protogonodon be removed from the family, the tooth characters may 
be defined as follows: 
Dental characters of the Phenacodontide. First and second upper molars 
quadrate and consisting of four principal cusps and two intermediates, no 
marked tendency toward the formation of a metaloph but the conules often 
uniting with the protocone to form a V; third upper molar always somewhat 
reduced and differing in outline from the other two molars because of the 
reduction of the metacone, the hypocone, or both; . first and second lower 
molars composed of four principal cusps, subequal in size, and a prominent 
1 Amer. Nat., 1893, p. 377. 
329 
