BONES OF THE SKULL — CRANIUM 



167 



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 cerebral surface of the squamous part is united 

 with the parietal bones, but a ventral 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 pro- 

 ject almost straight ventrally. The hypoglossal foramen is at the medial side of 

 the root of the process. The basilar part is short and wide; its ventral surface 



sj - 



Fig. 177. — Skull of Pig; Lateral View. 

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

 bone; G', maxilla; H, premaxilla; /, nasal bone; J, os rostri; K, mandible; 1, occipital condyle; 2, paramastoid proc- 

 ess; 3, condyle of mandible; 4, meatus acusticus externus; 5, temporal fossa; 6, parietal crest; 7, supraorbital process; 

 8, orbital part of frontal bone; 9, fossa for origin of ventral oblique muscle of eyeball; 10, orbital opening of supraorbital 

 canal; 11, lacrimal foramina; 12, supraorbital foramen and groove; 13, infraorbital foramen; 14, zygomatic process of 

 temporal bone; 15, temporal, and 15', zygomatic, process of malar bone; 16, incisor teeth; 17, canine teetli; 18, IS', 

 premolars; 19, 19', molars; 20, mental foramina; 21, mental prominence; 22, angle of mandible. 



bears a thin median ridge and two lateral imprints or tubercles which converge at 

 the junction with the sphenoid bone. 



The interparietal bone fuses before birth with the occipital. The internal 

 occipital protuberance is absent. 



The parietal bone is overlapped by the occipital bone behind and concurs in the 

 formation of the nuchal crest. Its external surface is divided by the parietal crest 

 into two parts. The medial part (Planum parietale) faces upward and forward, 

 and is flattened and smooth. Its medial border is short and straight and unites 

 early with the opposite bone. Its anterior border is concave and joins the frontal 



