oscoop] SCAPHOCEROS TYRRELLI EAS 
overhanging the lacrymal fossz., Lacrymal fosse about the same 
depth as in Ovibos but the shelves above them, instead of being at 
right angles to the axis of the skull, run diagonally from the orbits 
to the frontals, ending on the sides of the frontals in the plane of 
the posterior ends of the nasals. Orbits but slightly produced and 
scarcely projecting beyond the zygomata, even less tubular than 
in Bison, and differing widely from the much produced form of 
Ovibos. 
The posterior aspect of the skull is quite different from that of 
Ovibos. This is largely produced by a more decided constriction 
of the bony mass of the parietals beneath the horn cores and a more 
highly developed lambdoid crest. The mastoid width is therefore 
relatively much greater than the width immediately below the horn 
cores. Supraoccipital more excavated and occipital condyles more 
projecting; foramen magnum decidedly larger both actually and 
relatively; the occipital condyles much larger, wider, and more 
produced; basioccipital widely different, its sides not parallel nor 
nearly so, median line grooved instead of having a high trenchant 
median ridge. Auditory capsules apparently smaller; meatus larger 
and less deflected backwards. Posterior nares much wider and 
more flaring, the alisphenoid walls particularly larger and apparently 
somewhat arcuate instead of nearly straight in posterior outline. 
Palatine likewise larger and more expanded laterally, decidedly 
swollen just behind the plane of the last molar; sphenopalatine 
foramen much larger and more elliptical in shape (greatest diameter 
42 mm.). Vomer much larger and more swollen. Postglenoid 
process strongly deflected backward instead of being nearly at a 
right angle to the axis of the skull. The palatal parts of the maxil- 
laries curve gently from side to side but do not show the strong 
depression anteriorly that is found in Ovibos. The divided orifice 
of the parietotemporal canal is very large and placed relatively far 
back so that it is nearly midway between the lambdoid crest and the 
anterior border of the glenoid facet. Malar large and heavy though 
not inflated about the orbit as in Ovibos being merely produced into 
a heavy roughened ridge from which it spreads out on the face to 
join the maxillary. Facial part of lacrymal relatively more exten- 
sive; just below the prominent lacrymal fossa and immediately in 
front of the rim of the orbit is a slight depression or possible 
tendency to a secondary fossa. Lacrymal protuberance in the bot- 
tom of the orbit much larger than that of Ovibos and entirely differ- 
ent in shape; it is flattened below and ends posteriorly in a thin 
lamella on a plane with the posterior border of the sphenopalatine 
