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 
Fic. 177.—Sxkc tt or Pie; Lateran VIEw. 
A, Occipital bone; B, squamous temporal bone; C, parietal bone; D, frontal bone; EF, lacrimal bone; F, malar 
bone; G, maxilla; H, premaxilla; 7, 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 
eanal; 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 teeth; 18, 18’, 
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 
