1915.]: M aithew and Granger, Lower Eocene Wasatch and Wind River Faunas. ge 
Dentition. The anterior teeth cannot be determined with certainty. 
There is a pair of large, stout, oval canines, apparently little curved, and in 
front of them are at least two unusually large incisive alveoli. The first 
two premolars are indeterminate, the third is of moderate size without 
inner cusp but triangular in outline. The fourth premolar has a triangular 
protocone, strong, well separated deuterocone, external, internal and 
posterior cingula. The true 
molars are of subquadrate 
outline, one-fourth greater 
in transverse than in antero- 
posterior diameter, with low 
rounded conic cusps of equal 
height and an encircling cin- 
gulum. The second molar 
is a little larger than the 
first, the third much smaller. 
Paracone and metacone are 
close to the external margin, 
rounded, protocone more 
trihedral, metaconule mod- 
erately developed, para- 
conule rudimentary, hypo- 
cone prominent and distinct, 
extended anteriorly on m'? 
in a strong shelf internal to 
the protocone. — In all three 
the hypocone is developed 
from the internal cingulum. 
The measurements of the 
skull and teeth are about 
one-fifth greater than those 
of Vulp satiate a rof eclus, while Fig.8. Thryptacodon olseni, parts of fore limb: ante- 
the limbs are about one-half rior view of distal ends of humerus and radius, dorsal 
view of metacarpus, with unciform, lacking digit Ab i 
greater. Natural size, type specimen. 
Vertebre. The vertebree 
are at present so much buried in matrix that a detailed description is not 
possible. . 
Limb bones. The humerus is like that of Arctocyon and the Cercoleptoid : 
Miacidee. The deltoid crest is shorter and more abruptly ended than in 
Vulpavus, the radius facet less convex from side to side. 
The femur has a third trochanter, but quite small. The patellar trochlea 
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