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STEWART: OSTEOLOGY OF BISON ANTIQUUS LEIDY. ie a 
pre-sphenoid portion is not so sharply keeled as in Bos /aurus, nor is 
the deep sharp groove, just posterior to this portion, so prominent 
as in the species just mentioned. The orbito- and allisphenoids are 
not sufficiently well preserved to determine their characters or give 
comparisons with the recent forms. 
Periotic. 
The mastoid portion is broad and wedged in between the squa- 
mosals and ex oceipitals as in both of the recent forms mentioned. 
The superior portion, which forms the floor of the temporal fossa, 
is directed more outward than in Bison americanus, and the ridge, 
which extends along the external border and represents the lower 
continuation of the lambdoid crest, is not so sharp as in the recent 
ox, but is more rounded and roughened for ligamentary attachment 
as in Bison americanus. The tubercle, just above the meatus audi- 
torus externus, which is so prominentin Bos, has become much less 
marked and is somewhat roughened as in the recent bison. The 
anterior portion, just external to the glenoid cavity, is much more 
concave, but does not project downward so strongly as in wees; OT 
does the internal portion project outward to form a pit for the 
hyoid bone. 
The tympanic is much inflated from before backward and is 
more closely applied to the basi-occipital than in Aes, causing the 
external openings of the carotid canal and lacerated foramen to be 
very much compressed. The anterior styliform process is very 
short, even more so than in Bison americanus. 
Squamosal 
So far as can be determined the squamosals are very similar to 
the corresponding portions of the two species with which it was 
compared, except that the glenoid cavity is not so flat and the post- 
glenoid foramen is more laterally situated than in Aoy. 
Jugal. 
The posterior portions of the jugals are not preserved, but they 
were probably long and slender and extended almost to the glenoid 
Cavity as in both of the recent forms. The anterior orbital portion 
is more strongly projected outward and overhanging the face than 
in either of the forms mentioned, and the rim is much roughened 
for muscular attachment. The infra-orbital ridge, which is so well 
marked in both of the recent forms, is not present in this species. 
Frontals 
Che facial portion presents many points of difference when com 
bared with Bos taurus, but in most respects it 1s very similar to the 
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