580 REPTILES. 



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 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 may also 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. 



When a venomous snake strikes, the mandible is lowered, 

 the distal end of the quadrate is thrust forward, this 



