430 REPTILIA ORDER IV.RHYNCHOCEPHALIA. 



total distinctness from that order. Accordingly, the tuatera, which is tech- 

 nically known as Sphenodon pundatus, not only represents by itself the 

 family Sphenodontidee, but also a distinct order. This, however, is only true 

 at the present day, for in past epochs of the earth's history there flourished 

 a number of reptiles evidently belonging to the same ordinal group, several 

 of which lived in Britain. The tuatera, which grows to a length of about 

 twenty inches, is characterised by the presence of a ridge of spines extend- 

 ing from the back of the head to the base of the tail, and represented on the 



latter by a less distinct crest. 

 Superiorly, the body is covered 

 with a mixture of small tubercles 

 and granular scales ; but the lower 

 aspect is invested with somewhat 

 quadrangular large scales forming 

 regular transverse bands. The 

 toes, which are five in number on 

 each foot, are partially webbed, and 

 Fig. 28. TUATERA (Sphenodon pundatus). terminate in claws. In the eye 



the pupil takes the form of a ver- 

 tical slit, and there is no external opening to the ear. None of these fea- 

 tures are, however, sufficient to distinguish the tuatera from the lizards ; and 

 to understand the distinction the skull must be examined. In the descrip- 

 tion of the Squamata it was stated that in all the members of that order the 

 quadrate-bone is loosely connected with the other bonefl of the palate, and 

 there is no bony arch connecting the former with the maxilla. On the 

 other hand, in the tuatera the quadrate is firmly and immovably wedged in 

 between the other bones, and is connected with the upper jaw by the afore- 

 said arch. There are likewise important differences in the structure of the 

 bony palate, which is of a more primitive type than that of the lizards. 

 Indeed, in many respects the skull is more like that of a crocodile, or even a 

 tortoise, than that of a lizard. The teeth, too, are very peculiar. In the 

 front of the jaws are a pair of chisel-like teeth, giving the form of a beak to 

 this part of the skull : while the sides of the upper jaw and palate bear a 

 double row of closely approximated teeth separated by a groove, and in that 

 .groove are received the single row of lower teeth, which aro attached to the 

 jaw in the acrodont manner. Although there are many peculiar features in 

 this strange reptile, it will suffice to mention that within the skin of the 

 hinder part of the under surface of the body are a number of abdominal ribs, 

 forming a structure which corresponds anatomically with the plastron of a 

 tortoise. 



Although now becoming scarce, tuateras were formerly abundant in their 

 native islands, where they might be seen in parties basking in the sun 

 within easy reach of the sea. In captivity, where they flourish well, tuateras 

 eat freely of meal-worms and other insects, but it is probable that vegetable 

 substances form a part of their diet. Perhaps the most remarkable feature 

 about this reptile is the vestige of an unpaired median eye situated deep 

 down among the tissues of the head, and now totally functionless. Doubt- 

 less, however, in its ancestors this eye was functional, so that the original 

 form may have been a veritable cyclops. 



