DENTITION 57 



several respects departs less markedly from the Colu- 

 brid type than our European Vipers. 



The poison fangs of the Viperidse appear to be 

 movable, folding in the mouth when at rest, and 

 erected, or even thrust forward, when ready to act. 

 This, however, is simply due to the mobility of the 

 maxillary bone, to which they are ankylosed as in 

 all other snakes. There are normally two equally- 

 developed fangs, close together and side by side, to 

 each maxillary, followed by several replacement fangs 

 loosely attached behind them, usually in two series of 

 four. When the two fangs are in situ, they of course 

 both function in the act of biting, although only one 

 is in relation with the single poison duct ; often, how- 

 ever, there is only one fang in position, either the 

 right or the left, the place of the other being indi- 

 cated by a shallow socket which will soon be filled by 

 one of the posterior reserve fangs moving forward and 

 becoming ankylosed to the bone. Snake-charmers 

 who extract the poison fangs of the snakes they use 

 for their performances have therefore to renew the 

 operation frequently, unless they amputate the bone 

 on which the fangs are inserted, an injury which the 

 creature does not long survive. 



The dentition of the snakes in which the maxillary 

 bone is not movable vertically falls under three 

 divisions : the Aglyphs, in which the teeth are all solid ; 

 the Opisthoglyphs, in which one or more (usually 

 two) of the hindermost teeth are provided with a 



