SKELETON OF MAMMALIA. 
63 
Fig. 27. 
Skull of a Dog, divided down the centre to show the 
internal structure. 
an, anterior nasal opening ; as, alisphenoid ; ho, basioccipital ; hs, hasi- 
sphenoid ; c, canine teeth ; cd, condyle ; ce, cribriform plate ; cp, coro- 
noid process ; exo, exoccipital ; fr, frontal ; h, hyoid j i, incisor teeth ; 
id, inferior dental canal ; interparietal ; m, molar teeth ; me, mes- 
ethmoid ; mx, maxilla ; na, nasal ; os, orbitosphenoid ; pa, parietal ; 
per, periotic ; pi, palatine 5 jmi, premolar teeth ; ^niix, premaxilla 5 
p>s, presphenoid ; pt, pterygoid ; s, 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 
