Chapter I 



THE RHYNCHOCEPHALIA 



Sphenodon punctatus, theTuatera Lizard of the Maoris, is, 

 as mentioned in the Introduction, the only living member 

 of a group of Reptiles otherwise known from fossil repre- 

 sentatives only, and there can be no doubt as to its being 

 the oldest living reptilian type. In spite of its lizard-like 

 form it is perhaps almost as closely related to the Tortoises 

 as to the Lizards, and in fact many authorities regard the 

 order into which this creature falls as having directly given 

 rise to the Tortoises and the Crocodiles. Externally the 

 Tuatera resembles those hzards known as Agamas and Igu- 

 anas, and was in fact originally referred to the former of 

 these families. It differs, however, from true lizards in 

 many anatomical features, the principal of these residing in 

 the fact that the temporal region is bridged over by two 

 bony arches, the lower of which is absent in lizards, and that, 

 in addition to the sternal apparatus, a supplementary system 

 of numerous bones, so-called " abdominal ribs," fore- 

 shadows the plastron of Chelonians. A feature of Spheno- 

 don is its possession of the vestigial structure known as the 

 " pineal eye," an apparently functionless organ situated on 

 the top of the head, believed to represent the remains of a 

 once functional eye. 



5 



