THE SKULL. 



53 



mandible. This fossa is bounded caudally by the prominent 

 postman dibular process (;;/). 



All that portion of the lateral surface of the skull which lies 

 craniodorsad of the lambdoidal ridge may be divided (exclud- 

 ing the zygomatic arch) into three main parts, the temporal 

 fossa, the orbital fossa, and the face. The boundaries of the 

 temporal fossa have been given. The orbital fossa is bounded 



FIG. 40. SKUI.L, SIDE VIEW. 



I, occipital bone; 2, interparietal ; 3, parietal; 4, temporal; 5, 5', frontal; 6, 

 malar; 7, sphenoid; 8, palatine; 9, presphenoid; IO, maxillary; II. nasal; 12, pre- 

 maxillary; 13, incisor teeth; 14, canine; 15, 16, 17, premolars; 18, molar, a, oc- 

 cipital condyle; b, external occipital crest; c, sagittal crest; d, lambdoidal ridge; e, 

 tympanic bulla; f, jugular process; g, mastoid process; h, stylo-mastoid foramen; t, 

 pit for tympanohyal bone; j, external auditory meatus; k, zygomatic process of tem- 

 poral bone; /, mandibular fossa; m, postmandibular process; M, zygomatic process 

 of the frontal; o, supraorbital margin; p, external pterygoid fossa; q, sphenopalatine 

 foramen; r, orbital fissure; s, internal pterygoid fossa; t, hamulus; u, foramen 

 ovale; v, foramen rotundum; w, optic foramen; x, opening of lachrymal canal; y, 

 infraorbital foramen. 



externally by a prominent semicircular ridge formed chiefly by 

 the zygomatic arch, the zygomatic process of the frontal (;/), 

 and the supraorbital arch (o) of the frontal, which may be 

 traced to the cranial root of the zygomatic arch. The orbital 

 fossa may be considered to end caudally and ventral ly at the 

 level of the optic foramen (iv) ; ventrad of it are certain smaller 

 fossae. Immediately ventrad is the long external pterygoid 

 fossa (/), from which arises part of the external pterygoid 

 muscle. This fossa begins at the sphenopalatine foramen (q} 

 and extends caudad to the orbital fissure (r); it is separated 

 by a ridge from the orbital fossa. Caudoventrad of the external 



