AND TEETH OF THE OPISTHOaLYPHA. 301 



posterior one is lunged. It often happens that either the two 

 or three consecutive teetii drop out from the dried bones. This 

 is due to the fact that one of the fixed teeth is being replaced. 



The function of such an arrangement is difficult to determine, 

 but it seems to provide a firmer grip for the prey. While the 

 prey is being taken into the mouth and forced towards the 

 gullet, these hinged teeth, which point inward and backward, 

 bend down ; so that when tlie prey is struggling to escape from 

 the mouth, the teeth, being hinged, allow it to pass downwards 

 into the gullet but not outwards. Therefore from these 

 observations I am led to conclude that the hinged teeth are not 

 part of a series in the course of development which will become 

 ankylosed to the jaw, but that they will always remain hinged, 

 and during life will be held in place by the band of connective 

 tissue, while after death they may drop out. This opinion is 

 further emphasized by the facts that : firstly, in the maxillje and 



Text-figure 4. 



Tropidonotus stolatus. Longitudinal section of maxilla, showing a loose tooth with 

 its connective-tissue attacliment. I. ligament; m. maxilla; t. tooth. X 260. 



mandibles of the dried skull of the adult we can clearly see the 

 plane facets at the anterior end of the sockets, which show that 

 it has been subjected to constant friction ; secondly, if the tooth 

 were to be later ankylosed to the jaw-bone, there would be no 

 necessity for the inbending of the anterior end of its base ; 

 thirdly, it is inconceivable that in the numerous cases I have 

 examined, every second tooth should become worn out or drop 

 out accidentally. 



The grooved fangs are always placed at the posterior end of 

 the maxilla. Sometimes they are situated far back in the mouth, 

 so that their points are quite hidden within the angle of the jaw. 

 In this case the teeth are considerably bent (Bipsas), but where 

 they are a little more forward in the mouth they are generally 

 straighter. In shape they may be either flattened (Oxyhelis) or 

 circular (Psammophis), or may have a cutting-edge developed at 

 the posterior region. The grooves are either placed in the 



