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 liind-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 (J Hat. 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 low^er 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 
