62 LAND MAMMALS IN THE WESTERN HEMISPHERE 



and second, it carries the teeth and, by its movable jaws, 

 enables these to bite, to take in and masticate food. The 

 portion of the skull which carries the brain, eyes and ears, is 

 called the cranium, and the portion in front of this is the face, 

 the boundary between the two being an oblique line drawn 

 immediately in front of the eye-socket (Fig. 7). A great 



Ex.0. 



19 



mas 



p OC 



Fig. 7. — Skull of Wolf (Canis occidentalis). P.Mx., premaxillary. il/x., maxillary. 

 Na., nasal. L., lachrymal. Ma., malar or jugal. Fr., frontal. Pa., parietal. 

 Sq., squamosal. Zyg., zygomatic process of squamosal. O.S., orbitosphenoid. 

 PL, palatine. M., mandible, cor., coronoid process of mandible, m.c, condyle 

 of mandible, ang., angular process of mandible, p.g., postglenoid process of 

 squamosal. Ty., tympanic (auditory bulla), was., mastoid, p.oc, paroccipital 

 process, con., occipital condyle. Ex.0., exoccipital. S.O., supraoccipital. 



deal of the endless variety in the form of the skull of different 

 mammals depends upon the differing proportions of cranium 

 and face. In the human skull, for example, the cranium is 

 enormously developed and forms a great dome, while the face 

 is shortened almost to the limit of possibility ; the skull of the 

 Horse, on the other hand, goes to nearly the opposite extreme 

 of elongation of the facial and shortening of the cranial region. 

 The posterior surface of the skull, or occiput, is made up of 

 four bones, which in most adult mammals are fused into a 

 single occipital bone. At the base of the occiput is a large 

 opening, the foramen magnum, through which the spinal cord 

 passes to its junction with the brain ; and on each side of the 

 opening is a large, smooth, oval prominence, the occipital 

 condyles, by means of which the skull is articulated with the 



