XII 



PHYLUM CIIORDATA 





435 



of small claw-like processes. The mouth of the Snake is 

 capable of being very widely opened by the free articulation 

 of the lower jaw, and it is this mainly which distinguishes 

 it from the snake- 

 like Lizards. But 

 other, less conspic- 

 uous, points of dis- 

 tinction are the 

 absence of mov- 

 able eyelids in the 

 Snake, and also 

 the absence of a 

 tympanum. 



Hatteria,theNew 

 Zealand Tuatara 

 (Fig. 246), the only 

 living representa- 

 tive of the Rhyn- 

 chocephalia, is a 

 Lizard-like Reptile 

 with a well-de- 

 veloped, laterally- 

 compressed tail, 

 and pentadactyle 

 extremities very 

 similar to those of 

 a typical Lizard. 

 The upper surface 

 is covered with 

 small granular 



scales, and a crest of compressed spine-like scales runs along 

 the middle of the dorsal surface. The lower surface is 

 covered with transverse rows of large squarish plates. 



F F 2 



