174 SMITHSONIAN MISCELLANEOUS COLLECTIONS [voL. 48 
seum, Mr. Witmer Stone, of the Academy of Natural Sciences of 
Philadelphia, and Dr. J. A. Allen, of the American Museum of 
Natural History. To Mr. Stone I am particularly grateful for the 
loan of the valuable types of O. cavifrons and B. bombifrons. For 
assistance in handling specimens, thanks are due Mr. Walter L. 
Hahn, Aid, Division of Mammals, U. S. National Museum. 
SCAPHOCEROS TYRRELLI gen. et sp. nov. 
Type from 70 feet below the surface in gravels in Lovett Gulch, 
Bonanza Creek, Klondike District, Yukon Territory, Canada. No. 
2,555, U. S. National Museum. Male, old. Received from J. B. 
Tyrrell. 
Generic Characters.—Similar to Ovibos, but horn cores much 
smaller, less compressed at base, and more divergent at tips; crown 
of skull between bases of horn cores surmounted by a prominent 
exostosis with an anterior bounding rim and a deep median excava- 
tion; orbits much less produced laterally than in Ovibos; facial part 
of skull nearly as wide as cranial ; basioccipital without a high median 
ridge; teeth very large and relatively broad; m! and m2 quadrate in 
transverse view. 
Specific Characters.—Size smaller than in S. cavifrons (Leidy) ; 
horn cores much smaller and shorter; exostosis less extensive but - 
more deeply excavated; depth of braincase and surmounting bony 
mass decidedly less. 
Comparison with Ovibos moschatus.—Skull longer and of more 
uniform width than that of Ovibos moschatus, the facial region not 
abruptly narrower than the cranial. This gives the skulls of the 
two genera very different outlines, particularly as viewed from 
above, for while Scaphoceros is narrower than Ovibos across the 
orbits, it is wider between the maxillaries. Anterior part of skull 
much elongated, although not narrowed abruptly as in Ovtbos; 
maxillaries and premaxillaries much longer. The ascending branch 
of the premaxillary apparently does not reach the nasals but ends 
in nearly the same relative position as in Ovibos but at an angle 
of lesser degree, since it does not turn up so abruptly. Exposed 
part of frontals, not covered by exostosis, much less extensive but 
suture with nasals apparently in same relative position in plane of 
front of orbits. This exposed part of the frontals is much nar- 
rower and more elevated between the orbits, but notwithstanding 
this, the groove between the elevated median part and the orbits 
is much less pronounced and does not appear to extend to the shelf 
