_I_, Occipital; _II_, parietal; _III_, frontal; _IV_, lacrimal; _V_,
malar; _VI_, squamous temporal; _VII_, nasal; _VIII_, maxilla; _IX_,
premaxilla; _1_, supraoccipital; _2_, interparietal; _3_,
parieto-occipital suture; _4_, occipital crest; _5_, sagittal crest;
_6_, parieto-frontal suture; _7_, squamous suture; _8_, parietal
eminence; _9_, antero-external angle of parietal bone; _10_, frontal
crest; _11_, _14_, orbital margin; _12_, supraorbital process; _13_,
frontal fossa; _15_, temporal part of frontal bone; _16_, nasal
process of frontal bone; _17_, frontal suture; _18_, lacrimal
foramen; _19_, maxillary process of frontal bone; _20_,
lacrimo-maxillary suture; _21_, frontal process of malar bone; _22_,
lacrimal process of malar; _23_, zygomatic process of malar; _24_,
zygomatic process of squamous temporal; _24′_, posterior end of
nasal bone; _25_, nasal suture; _26_, anterior end of nasal bone;
_27_, infraorbital foramen; _28_, canine tooth; _29_, cheek tooth;
_30_, frontal process of maxilla; _31_, body, _32_, nasal process,
_33_, palatine process of premaxilla; _34_, palatine fissure; _35_,
incisor teeth. (Ellenberger-Baum, Anat. d. Hundes.)
]
The =parietal bone= is rhomboid in outline and is strongly curved. It is
extensive and forms the greater part of the roof of the cranial cavity.
At the junction of the right and left bones there is a prominent
sagittal crest which is continued upon the frontal bones. The lower
border articulates with the temporal wing of the sphenoid by its
anterior part and with the squamous temporal in the remainder of its
extent. The external surface enters into the formation of the temporal
fossa. The internal surface is marked by digital impressions, and by
grooves for the middle meningeal artery and its branches.
The external surface of the =frontal bone= is crossed by a frontal
crest, which extends in a curve from the sagittal crest to the
supraorbital process, and separates the frontal and temporal parts. The
frontal parts of the two bones form a central depression and slope
downward and forward. The supraorbital process is very short, so that
the orbital margin is incomplete as in the pig. The supraorbital foramen
is absent. In front there is a narrow pointed nasal part which fits in
between the nasal bone and the maxilla. The orbital and temporal parts
are relatively extensive. Two ethmoidal foramina are commonly present.
The frontal sinus is confined to the frontal bone.
The parts of the =temporal bone= fuse early. The zygomatic process
curves widely outward and forward. Its anterior part is beveled below
and articulates extensively with the corresponding process of the malar.
The articular surface for the condyle of the mandible consists of a
transverse groove which is continued upon the front of the large
postglenoid process. Behind the latter is the lower opening of the
parieto-temporal canal. There is no condyle. The mastoid part is small,
but bears a distinct mastoid process. The external auditory meatus is
large and the canal very short, so that one can see into the tympanum in
the dry skull. The India ossea is very large and is rounded and smooth;
the inner side is united to the basioccipital. Above this junction and
roofed in by the union of the petrous part and the basioccipital is the
=petro-basilar canal= (Canalis petrobasilaris); this transmits a vein
from the floor of the cranium to the foramen lacerum posterius. The
latter is in reality a depression and is situated behind the bulla
ossea. In its posterior part is a foramen which transmits the ninth,
tenth, and eleventh cranial nerves. The =carotid canal= branches off
from the petro-basilar, passes forward external to it through the inner
part of the bulla ossea, and opens in front at the =carotid foramen=; it
transmits the internal carotid artery. The Eustachian opening is
immediately external to the carotid foramen. The muscular and hyoid
processes are extremely rudimentary. The petrous part projects into the
cranial cavity and forms a sharp prominent petrosal crest. The inner
surface presents a deep =floccular fossa= above the internal auditory
meatus. The anterior surface is also free. The anterior angle is
perforated by a =canal= for the fifth cranial nerve (Canalis nervi
trigemini).
[Illustration: