SKELETON OF MAMMALIA. 



63 



Fig. 27. 



an 



pmx 



id 



Skull of a Dog, divided down the centre to show the 

 internal structure. 



an, anterior nasal opening ; as, alisphenoid ; bo, basioccipital ; bs, basi- 

 sphenoid ; c, canine teeth ; cd, condyle j ce, cribriform plate ; cp, coro- 

 noid process ; exo, exoccipital ; fr, frontal ; h, hyoid ; i, incisor teeth ; 

 id, inferior dental canal ; ip, interparietal ; m, molar teeth ; me, mes- 

 ethmoid ; mx, maxilla ; na, nasal ; os, orbitosphenoid ; pa, parietal ; 

 per, periotic ; pi, palatine ; pm, premolar teeth ; pmx, preniaxilla ; 

 ps, presphenoid ; pt, pterygoid ; s f symphysis of mandible ; so, supra- 

 orbital; t, turbinal ; vo, vomer; the asterisk indicates the part of the 

 cranium to which the lower jaw is articulated. 



brain, and a support and protection to the organs of smell, sight, 

 hearing, and taste ; (2) the mandible, or lower jaw ; and (3) the 

 hyoid arch, or tongue-bones. 



The cranium forms in its posterior half a large hollow case for 

 the reception of the brain, and has along its base numerous perfo- 

 rations, or foramina, for the passage of the nerves and blood- 

 vessels ; in front of this case, and separated from it by a sieve- 

 like bone, the cribriform plate (fig. 27, ce), there is a bony tube, 

 open in front at the anterior nares (an), filled with light spongy 



