1888.] 69 [Cope. 
three postpariétal foramina, the inferior small and on the squamosal 
suture. The mastoid foramen is small, is anterior to the lateral occipital 
crest, and is apparently on a suture. There are two supraglenoid fora- 
mina, both small, the larger on the inner side of the base of the zygoma. 
The meatus auditorius eaternus is small, and is directed upwards and out- 
wards. There is a foramen on the inner aspect of the line of contact of 
the posttympanic and postglenoid plates, which is probably continuous 
with the postglenoid. The stylomastoid foramen is, externally at least, 
longer than the postglenoid. The superior border of the foramen mag- 
num is an open angle. 
Of the superior incisor teeth only the third is preserved. The crown is 
oval and of moderate width. There were two inferior incisors in each 
ramus. Of the presence of a third Iam very doubtful. They have rather 
narrow truncate crowns of equal width, and are directed upwards at an 
angle of 45°. The canines are robust. They have a subtriangular sec- 
tion, but the inferior triangle has a truncated (anterior) apex. These teeth 
differ from those of B. pristinus and B. trichanus in having two grooves 
separated by a ridge on the external sides, instead of one groove. The 
narrow anterior face of the inferior canine is also shallowly grooved. 
The fourth superior premolar is almost entirely within the superior ca- 
nine. It is small, but two-rooted. The third is much longer, and is much 
compressed. The second is but little longer than the third. Its crown 
consists of a single compressed cusp, with an internal cingulum which 
expands posteriorly, enclosing a narrow basin, and turning outwards forms 
a narrow basal heel. The first premolar has a base wider than long. Its 
external tubercle is bifid, the principal one supporting a rudiment of a 
second, The internal cusp is connected with the external by a transverse 
ridge, which does not reach the apex of the latter. A wide cingulum 
forms the internal and posterior outline of the crown. A narrow external, 
and no internal cingulum. The true molars are subquadrate in form, 
and increase in size posteriorly. The first is not so reduced in relative 
proportions as in the Chanohyus decedens. The external cusps are a little 
flattened externally, not so conspicuously as in the last-named species. 
Intermediate tubercles are present as in that species. An anterior and a 
posterior, a faint external and no internal cingula. The posterior cingu- 
lum is wide in the second molar and supports a rudimental third interme- 
diate tubercle. In the third true molar it is wider and has a plicate border, 
but no considerable cusp. The second transverse series of tubercles of 
this tooth consists of those tubercles besides the intermediate tubercle in 
front of it, instead of two as exhibited by the other species. The external 
tubercle of this series is flattened on the external side. The intermediate 
tubercle of the first row is large and distinct. The crowns of the inferior 
molar teeth are not visible in this specimen. It can be seen, however, 
that the only diastemata in the series are very short, and are anterior and 
Posterior to the fourth one-rooted premolar. 
