GENERAL NOTES ON SNAKES. 579 



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 effected, 

 and thus the serpent flows onward. But this account of the 

 mechanism of movement 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 dissolution 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 may also be movable. On the other hand, the 

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

 premaxillte are very small and rarely bare 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 Dasypeltis the teeth are 

 rudimentary, but the inferior spines of some of the anterior 



