26 1 8 



THE REMAINING GROUPS OF REPTILES 



the latter being more or less completely worn away in extreme old age. On the up- 

 per surface of the skull is a large vacuity or foramen in the parietal bones. In ex- 

 ternal appearance the tuatera is lizard-like, the body being slightly and the long tail 

 strongly compressed; the limbs carry five toes, all furnished with claws, and con- 

 nected 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 or the head down the middle of the back, continued in a 

 smaller degree of development down the tail; while inferiorly there are large 

 squarish scales arranged in transverse rows. Attaining a length of about twenty 

 inches, the tuatera is olive or blackish in ground color, upon which are small yel- 

 lowish dots, and the lobes of the crest on 

 the neck and back are likewise of the latter 

 color. The perforation in the parietal bones 

 of the skull just referred to covers a rudi- 

 mentary eye, which, although now func- 

 tionless, was probably a working organ in 

 the ancestors of the Vertebrates. In the 

 young tuatera this pineal eye can be seen 

 through the translucent skin, but in the 

 adult this skin becomes opaque. 



In the Jurassic rocks of 

 Allied _ 



c. ... Europe there occur remains 

 Families 



of reptiles allied to the tua- 

 tera, but constituting a distinct family (Ho- 

 mceosauridtf} typically represented by the 

 genus Homceosaurus. These have no tusk- 

 like teeth in the front of the jaws, and the 

 lower end of the humerus has a perforation 

 only on its inner side, and there are no in- 

 tercentra between the vertebrae of the back, 

 and no hook-like processes to the ribs. A 

 third family {Rhynchosaurida) is typified 

 by the genus Rhynchosaurus from the 

 Trias or New Red Sandstone of England, 

 and is characterized by the beak being 

 toothless and probably sheathed in horn; 



the palate having two or more longitudinal rows of teeth separated by a groove. 

 From the preceding families these reptiles differ by having only a single aperture to 

 the nostrils, and by the bony union of the two branches of the lower jaw; while the 

 articular surfaces of the vertebrae are nearly flat. Moreover, there is no vacuity in 

 the middle of the top of the skull. In the typical genus there is a single row of 

 teeth on the inner side of the groove on the palate, but in the Hyperodapedon there 

 were numerous rows, as is shown in the illustration. The extremity of the beak 

 in each jaw formed two curved tusk-like processes, which diverged in the lower one. 



OF THE Hyperodapedon. 

 (One-fourth natural size.) 



The upper figure shows the superior aspect; the 

 lower one on the left the palate, and the right 

 lower one the under surface of the front of the 

 lower jaw. 



