48o REPTILES. 



The serpent " literally rows on the earth, with every scale 

 for an oar ; it bites the dust with the ridges of its body." On 

 a perfectly smooth surface it can make no headway, but in 

 normal conditions the edges of the anterior ventral scales 

 are fixed against the roughnesses of the ground, the ribs are 

 drawn together first on one side then on another, the body 

 is thus wriggled forward to the place of attachment, the 

 front part shoots out as the hind part fixes itself, an 

 anterior attachment is again eifected, and thus the serpent 

 flows onward. But this account of the mechanism of move- 

 ment, does not suggest the swiftness or the beauty of what 

 Ruskin calls " one soundless, causeless march of sequent^ 

 rings, and spectral procession of spotted dust, with dissolu- 

 tion in its fangs, dislocation in its coils." " Startle it ; the 

 winding stream will become a twisted arrow ; — ^^the wave of 

 poisoned life will lash through the grass like a cast lance." 



One of the most distinctive characteristics of the skull, is 

 the mobility of some of the bones. Many of the Ophidians 

 swallow animals which are larger than the normal size of the 

 mouth and throat. The mobility of the skull bones is an 

 adaptation to this habit. Thus, the rami of the mandible 

 are united by an elastic ligament ; the quadrates and the 

 squamosals are also movable, forming " a kind of jointed 

 lever, the straightening of which permits of the separation 

 of the mandibles from the base of the skull." The nasal 

 region also may be movable. On the other hand, the 

 bones of the brain-case proper are firmly united. The 

 premaxillae are very small and rarely bear teeth; the 

 palatines are usually connected with the maxillae by trans- 

 verse bones, and through the pterygoids with the movable 

 quadrates. 



Teeth, fused to the bones -which bear them, occur on the 

 dentaries beneath, and above on the maxillae, palatines, and 

 pterygoids, and very rarely on the premaxillae. The fang-like 

 teeth of venomous serpents are borne by the maxillae, and are 

 few in number. Each fang has a groove or canal down which 

 the poison flows. When the functional fangs are broken, they 

 are replaced by reserve fangs which lie behind them. In the 

 egg-eating African Rachiodon the teeth are rudimentary, but 

 the inferior spines of some of the anterior vertebrae project on 

 the dorsal wall of the gullet, and serve to break the egg-shells. 



