176 SMITHSONIAN MISCELLANEOUS COLLECTIONS [vou. 48 
foramen. The flattened lower surface of this protuberance is almost 
horizontal and parallel to the main axis of the skull. It is evidently 
an important character, differing widely, as it does, from the same 
structure in Ovibos, Bos, Bison, and Ovits. 
Horn Cores and Exostosis——In the type specimen which is evi- 
dently a very old male, the horn cores relative to the size of the 
skull and in comparison with those of adult male Ovibos are very 
slender. At their bases the antero-posterior expansion is compara- 
tively slight. Although the vertical diameter of the horn cores is 
less at any point than the horizontal diameter, there is in comparison 
with the horn cores of Ovibos a decided tendency toward round- 
ness. A cross section of the horn core near the base would be ellip- 
tical but a section taken four inches from the base would be more 
nearly ovoid. The direction of the cores although somewhat down- 
ward is distinctly away from the skull, and the tips are directed 
forward. 
Between the bases of the horn cores and for some distance anterior 
to them is a roughened and much perforated bony growth or exos- 
tosis occupying the greater part of the crown of the skull. In Ovibos 
there is a somewhat similar growth, which, however, is all on the 
same plane with the top of the horn cores, is but slightly produced 
anteriorly, and is always divided by a deep median channel the floor 
of which is continuous with the normal surface of the frontals. In 
Scaphoceros this exostosis is depressed between the horns forming 
an oblong excavation bounded laterally by the bases of the horn 
cores and anteriorly by a rugose shelf-like rim which is elevated 
like a crown over the frontals and the base of the orbits. Posteriorly 
the depression is open though there are evidences that it may have 
been inclosed by a rim similar to the anterior one. Fully a third of 
the exostosis and depression is anterior to the plane of the front of 
the bases of the horn cores so that the anterior bounding shelf 
reaches almost to the plane of the front of the orbits. The anterior 
boundary shows no evidence of a median division, but the de- 
pression appears to have been traversed by a median ridge; in S. 
cavifrons this ridge is more plainly shown. Possibly the horny 
sheaths that covered the exostosis in the living animal were com- 
pletely united. At least it is safe to assume that the two sides were 
more closely apposed than in Ovibos, and that the horn sheaths 
were shaped very differently at the base. 
Teeth.—The teeth of Scaphoceros are actually larger than those 
of Bison bison. In size and shape they differ widely from those of 
Ovibos but in structure appear to be quite similar. Their propor- 
