_F_, Pterygoid bone; _G_, horizontal and _G′_, perpendicular part of palate bone; _H_, occipital bone; _J_, malar bone; _K_, sphenoid bone; _O_, maxilla; _P_, vomer; _Sch._, squamous temporal; _St._, frontal bone; _Z_, premaxilla; _1_, for. magnum; _2_, occipital condyle; _3_, paramastoid (styloid) process of occipital; _4_, hypoglossal and condyloid foramina; _5_, for. lacerum; _6_, pharyngeal tubercles; _7_, bulla ossea; _8_, muscular process (left one is removed to expose for. ovale); _9_, hyoid process; _10_, ext. auditory meatus; _11_, zygomatic process; _12_, external opening of parieto-temporal canal; _13_, postglenoid process; _14_, temporal condyle; _15_, for. ovale; _16_, for. lac. orbitale + for. rotundum; _17_, optic foramen; _18_, ethmoidal foramen; _19_, orbital opening of supraorbital canal; _20_, pterygoid crest; _21_, hamulus of pterygoid bone; _22_, lacrimal bulla; _23_, temporal process of malar; _24_, pterygoid process of maxilla; _25_, sphenopalatine foramen; _26_, maxillary foramen; _27_, posterior palatine foramen; _28_, anterior palatine foramen; _29_, accessory palatine foramina; _30_, palate process of maxilla; _31_, interalveolar border; _32_, palatine cleft; _33_, palate process of premaxilla; _34_, fissura incisiva; _35_, facial tuberosity; _36_, posterior nares. (Ellenberger-Baum, Anat. d. Haustiere.) ] The =parietal bones= do not enter into the formation of the roof of the cranium. They constitute the upper part of the posterior wall, and bend sharply forward along the lateral wall, forming part of the wall of the temporal fossa. The line of inflection is marked by the prominent =parietal crest=, which is continuous with the temporal crest below. The parietals are excavated to form part of the frontal sinuses in the adult animal. The condition in the young subject is as follows: The two parietals are united with each other and also with the interparietal and supraoccipital. The resulting mass is somewhat horseshoe-shaped. Its occipital part (Planum occipitale) forms the greater part of the posterior wall of the cranium and bears about its center the tuberosity for the attachment of the ligamentum nuchæ. From either side of this a line curves outward, and divides the surface into an upper smooth area and a lower area which is rough for muscular attachment. The upper border joins the frontal bone and concurs in the formation of the frontal eminence. The temporal parts (Plana temporalia) are much smaller and are concave externally; they join the frontal above and the squamous temporal below. [Illustration: FIG. 91.—SKULL OF OX, DORSAL VIEW (WITH MANDIBLE).