682 PROCEEDINGS OF THE NATIONAL MUSEUM. VOL. XXXIV. 
Type-locality—The Palisades, Yukon River, about 35 miles below 
Tanana, Alaska. 
[Torizon.—Pleistocene. 
Species characters.—Size of teeth somewhat larger, with the in- 
ternal median valley in the upper molars less infolded at base than 
in the living species O. moschatus, skull somewhat larger through- 
out; ascending process of the premaxillaries nearly or quite reaching 
the nasals; basisphenoid shghtly overlapped by the vomer; otic bulla 
greatly reduced, being intermediate in size between that of O. moscha- 
tus and Symbos tyrrella (Osgood) Osgood. The horn-cores droop in 
about the same degree as in the living species. (See fig. below.) 
_.The species further differs from O. moschatus as follows: (1) 
Posterior narial opening much larger; (2) spheno-palatine foramen 
S 
2 ASL = 
NS) 
\ \ ANE hy 
———w 
! 
LS 
. 
\ 
1 
S 
= Y 
7 a) 
1 
Ao 
Pp Ay 
3 
POSTERIOR VIEW OF CRANIUM OF OVIBOS YUKONENSIS. 
about one-third greater in diameter; (3) basioccipital proportionally 
wider, with a decidedly deeper and broader median fossa; (4) horn- 
cores more depressed at base; (5) frontals more arched in the median 
ne, owing to their greater depression on either side above the 
orbits; (6) the much greater anteroposterior width of the horn- 
cores; and (7) the presence of a regularly striated rugosity on the 
frontals, fringing the anterior borders of the horn-core bases. This 
last character may be an age condition only, but it indicates a for- 
ward expansion of the horn-covering and suggests a tendency to 
extend the horn-core base forward, as in Symbos. 
While there is no doubt regarding the generic reference of this 
species, in certain characters in which it differs from O. moschatus it 
appears to approach Symbos tyrrelli. These deviations are most 
