TUATERA. 



2 53 



by each segment of the shield on the lower surface of the body being formed of 

 only three elements, of which the middle one is chevron-shaped, and likewise by 

 the fifth metatarsal bone of the hind-foot being reduced in length and thickened 

 in the same manner as in lizards. The group is further characterised by the 

 double nostrils, the union of the two branches of the lower jaw by cartilage, and 

 the deeply hollowed articular surfaces of the vertebrae. From its extinct allies the 

 family is distinguished by having a perforation on each side of the lower 

 extremity of the humerus, or upper bone of the fore-limb ; by the presence of 

 hook-like processes to the ribs, as well as of so-called intercentra, or additional 

 segments between the bodies of the vertebrae; and likewise by the beak-like 

 premaxillary bones carrying a pair of somewhat chisel-like teeth, and the presence 



NEW ZEALAND TUATERA {\ liat. Size). 



of only a single row of teeth on the palate, which are separated by a groove from 

 the row affixed to the edge of the upper jaw. Into this groove is received the 

 teeth and upper edge of the lower jaw, which in very old individuals becomes as 

 hard and polished as the teeth themselves ; the latter being more or less completely 

 worn away in extreme old age. On the upper surface of the skull is a large 

 vacuity, or foramen, in the parietal bones. In external appearance the tuatera is 

 lizard-like, the body being slightly and the long tail strongly compressed ; while 

 the limbs carry five toes, all furnished with claws, and connected at their bases by 

 webs. There is no external opening to the ear, and the large eye has the pupil 

 vertical. On the upper-parts the creature is clothed with small granular scales, 

 intermixed with tubercles ; and a crest of spine-like scales runs from the hinder- 

 part of the head down the middle of the back, continued in a smaller degree of 



