The =thorax= is long and is more barrel-shaped than in the horse or ox, since the ribs are more strongly curved and differ less in relative length. [Illustration: FIG. 109.—SKULL OF PIG, LATERAL VIEW WITHOUT MANDIBLE. _1_, Occipital condyle; _2_, paramastoid or styloid process; _3_, bulla ossea; _4_, external auditory meatus, _5_, zygomatic process of temporal bone; _6_, sphenoid bone; _7_, orbital opening of supraorbital canal; _8_, malar bone; _9_, pterygoid bone; _10_, pterygoid process of sphenoid; _11_, pterygoid process of palate bone; _I1–3_, incisor teeth; _C_, canine tooth; _P1–4_, premolars; _M1–3_, molars. ] BONES OF THE SKULL CRANIUM The =occipital bone= has an extensive squamous part or supraoccipital, which forms a very broad and prominent crest. The latter is concave, and is thick and rough above, where it forms the highest part of the skull; laterally it becomes thinner, turns downward, and is continuous with the temporal crest. Two divergent ridges pass upward from the foramen magnum, and the surface between them is concave and smooth. The greater part of the inner (or anterior) surface of the supraoccipital is united with the parietal bones, but a lower concave area faces into the cranial cavity. The foramen magnum is almost triangular, and is narrow above, where it is flanked by two small tuberosities. The paramastoid processes are extremely long and project almost straight downward. The hypoglossal foramen is at the inner side of the root of the process. The basilar part is short and wide; its lower surface bears a thin median ridge and two lateral imprints or tubercles which converge at the junction with the sphenoid bone. [Illustration: FIG. 110.—SKULL OF PIG, DORSAL VIEW. ] The =interparietal= fuses before birth with the occipital. The tentorium osseum is absent. The =parietal= is overlapped by the occipital bone behind and concurs in the formation of the occipital crest. Its external surface is divided by the parietal crest into two parts. The inner part (Planum parietale) faces upward and forward, and is flattened and smooth. Its inner border is short and straight and unites early with the opposite bone. Its anterior border is concave and joins the frontal bone. The outer part (Planum temporale) faces outward and is more extensive; it is concave, forms a large part of the temporal fossa, and is overlapped below by the squamous temporal. The parietal crest extends in a curve from the occipital crest forward and outward to the supraorbital process. The internal surface is concave and is marked by digital impressions. The lower border projects into the cranial cavity and forms a crest which separates the cerebral and cerebellar compartments laterally. The interior forms part of the frontal sinus in the adult. There is no parieto-temporal canal.