1915.] Matthew and Granger, Lower Eocene Wasatch and Wind River Faunas. 7 
Vulpavus except that the unguals are longer, not quite so high and compressed, the 
sub-ungual processes heavier. 
The entocuneiform is as broad as in Vulpavus but lacks the characteristic asym- 
metry of that genus; it is broader than in Didymictis and decidedly broader than in 
Oxyeenidee. 
The middle caudals are long and heavy. 
Thryptacodon gen. nov. 
Type, T. antiquus, infra. 
Generic characters: Upper molars low-crowned, quadrate-oval or rounded, 
cusps round conic, hypocone prominent on m!~, enamel rugose, m3 somewhat reduced, 
round oval; p* trihedral with small deuterocone, distinct para-~ and metastyles. 
Lower molars broad with very small submedian paraconid and four sub-equal opposite 
principal cusps. Heavy external cingula on lower molars; heavy encircling cingula 
on upper molars. Anterior premolars slender; canines long, compressed and ridged 
posteriorly. Skull short with comparatively large brain-case, skeleton relatively 
large, resembling that of Miacine. | 
This genus is not rare in the lower horizons of ;the Big Horn Wasatch, 
but has not been found in the Lysite 
or Lost Cabin. It appears to be re- 
lated to Tricentes and Chriacus, but 
has more rounded teeth than the for- 
mer, m more reduced; differs from 
Chriacus in the lower cusps, broad 
“rounded teeth, rugose enamel and 
heavy cingula. It approaches the 
Arctocyonidse more nearly than do 
any other Oxy cleenids, but is less Spe Fig. 3. Thryptacodon olsen, upper teeth, 
cialized and the skull and skeleton are crown and external views, natural size. 
. No. 16163, Gray Bull beds, Big Horn Basin, 
more progressive. The very marked Wyoming. 
detailed resemblance to Clenodon in 
the construction of the molar teeth can hardly be interpreted otherwise than 
as proof of close affinity, and makes the propriety of separating Oxycleenidee 
and Arctocyonide as distinct families very questionable. There is a notable 
difference indeed in the form and proportions of the skull and in the pro- 
portions of the skeleton. But it is not as wide as between Didymictis and 
Palearctonyx in the Miacidee. 
In size and general proportions of the teeth these two species are not un- 
like Paleosinopa. The detail construction of the molars easily distinguishes 
the two genera. In Paleosinopa the cusps are decidedly higher, more 
angulate, the paraconid more prominent, placed nearer to the inner border, 
No. /6/63 
A. 14. 
