1915.] Matthew and Granger, Lower Eocene Wasatch and Wind River Faunas. 39 
Ten lower jaws from the Lost Cabin horizon of the Wind River agree 
very well with the types of canavus and brevirostris, which differ only in 
very trifling or inconstant characters. Five jaw fragments from the Lysite 
vary a little in innumerable details towards Miacis; and in five specimens 
from the Gray Bull horizon, these differences are more pronounced, the 
trigonid of m, being higher, the heels of m; and m,: narrower, the roots of m; 
imperfectly separated, the premolars relatively larger. Although insuffi- 
cient in degree to warrant a specific separation, these differences are signifi- 
cant in confirming the approach of these two Miacid genera as we trace 
them back through the Eocene. Differences of similar kind and equal 
degree are seen in specimens of the following species from the three horizons. 
Vulpavus australis sp. nov. 
Type, No. 16226, lower jaw with 
ps-m; from the Wasatch of New Mex- 
ico, ?lower beds. 
Distinctive characters: Smaller than 
V. canavus, mig = 15 mm.; canines 
less robust, teeth less massive, but very 
similar in constructive details. 
Four specimens from New Mex- 
ico, two from the Lost Cabin beds 
of Wyoming, five from the Lysite 
and four from the Gray Bull beds, 
are referred to this species. Those 
from the Gray Bull beds show a 
distinct approach toward Mzacis, 
as in V. canavus but the New Fig. 33. Vulpavus australis, lower jaw, 
s : é outer view and crown view of teeth enlarged 
Mexican specimens, Nos. 16225-7, to two diameters, with outline of natural size. 
16229, which except the type are all Type specimen, Wasatch of San Juan Basin, 
New Mexico. Dotted outlines restored from 
from the upper beds, agree nearly No. 16227. 
with the Lysite specimens. Nos. 
14764-5 from the Lost Cabin are somewhat more progressive towards the 
typical Vulpavus from the Middle Eocene. — 
Vassacyon Matthew 1909.' 
Type, V. promicrodon from the Wasatch of the Big Horn Basin. 
This genus is in many respects intermediate between Miacis and Vul- 
10. 8. G. 8. Bull 361, p. 93. 
