BONES OF THE SKULL — CRANIUM 



189 



The interparietal bone fuses with the occipital before birth. It bears the high 

 posterior part of the parietal crest, and is wedged in between the two parietal bones 

 It forms the central part of the tentorium osseum, which is thin and curved, con- 

 cave ventrally. Its base concurs with the occipital and parietal bones in the for- 

 mation of a transverse canal which is continuous with the temporal canals. 



The parietal bone is rhomboid in outline and is strongly curved. It is exten- 

 sive 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 parietal crest which is continued 

 upon the frontal bones. The ventral border articulates with the temporal wing 

 of the sphenoid by its anterior part and with the squamous temporal in the remain- 

 der of Its extent. The external surface enters into the formation of the temporal 



Fig. 208. — Skull of Dog; Lateral View. 

 A, Occipital bone; B, parietal bone; C, squamous temporal bone; D, frontal bone; E, lacrimal bone; F, malar 

 bone; G, perpendicular part of palatine bone; H, maxilla; /, premaxilla; J, nasal bone; K, mandible; 1, parietal 

 crest; 2, occipital condyle; 3, paramastoid process; 4, stylo-mastoid foramen; 5, bulla ossea; 6, meatus acusticua 

 externus; 7, external opening of temporal canal; 8, postglenoid process; 9, zygomatic process of temporal bone; 10, 

 zygomatic process of malar bone; 11, supraorbital process; 12, entrance to lacrimal canal; 13, infraorbital foramen; 

 14, mental foramina; 15, condyle of mandible; 16, coronoid process; 17, mandibular notch; 18, angular process; 19, 

 masseteric fossa; i. i', incisor teeth c, c', canine teeth. 



fossa. The cerebral 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 "parietal 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 supraorbital margin is incomplete as in the pig. The supraor- 

 bital 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 ventrally and articulates 



