460 MAMMALIAN ANATOMY 



nasal processes of the frontal above, the maxillary in the middle, and 

 the premaxillary below. These parts of the suture are named the 

 naso-frontal suture, the maxillo-nasal suture, and the premaxillo- 

 nasal suture respectively. The nasal bones included between the 

 sutures of the two sides of the face form a high triangular shield for 

 the anterior end of the nasal cavity. At the junction of the naso- 

 frontal and maxillo-nasal sutures, at the tip of the nasal process of the 

 maxillary, the fronto-maxillary suture curves upward and outward, 

 then downward and outward, and ends at the external angular pro- 

 cess of the frontal bone; it joins the upper arcuate end of the nasal 

 process of the maxillary to the frontal. At the junction of the maxillo- 

 nasal and premaxillo-nasal sutures is the upper end of the premaxillo- 

 maxillary suture, which curves downward and outward to end on the 

 lower border just medial to the canine tooth. On the inner maxillary 

 rim of the orbit is the lachrymal tubercle. Beneath the orbit, at the 

 inner side, is the infraorbital foramen, which transmits the infraorbital 

 nerve and artery. Directly above this foramen on the orbital rim is 

 the inner end of the malo-maxillary suture, which, running outward 

 and downward, joins the anterior or malar end of the zygoma to the 

 maxillary bone. 



The nasal aperture, or opening of the anterior uares, is median 

 and heart-shaped ; it is slightly wider than high, and is surrounded by 

 the nasal and premaxillary bones. When the skull is held with the 

 base horizontal, the upper end of the opening is on a level with the 

 lower rim of the orbit. It is separated from the mouth by a narrow 

 strip derived from the premaxillaries. Its lateral outline is encroached 

 upon above by the prominent external angular process of the nasal. 

 On each side below is the small inferior nasal spine on the premaxil- 

 lary. The margins of this opening are sharp above and rounded 

 below ; they give attachment to the external cartilages of the nose. 

 In the natural state the anterior end of the median cartilaginous nasal 

 septum converts the nasal aperture into the two equal and symmetrical 

 anterior nares. 



UPPER ASPECT OF THE SKULL. 



The upper aspect of the skull (Fig. 385) presents but few note- 

 worthy features. It may be conveniently studied if the base be placed 

 downward and the posterior end toward the student. The general 

 outline seen from above is oval ; its greatest length is two-sevenths 



