254 
BEAKED LIZARDS. 
development down the tail; while interiorly there are large squarish scales arranged 
in transverse rows. Attaining a length of about 20 inches, the tuatera is olive or 
blackish in ground-colour, upon which are small yellowish dots, while the lobes of 
the crest on the neck and back are likewise of the latter colour. The perforation 
in the parietal bones of the skull just referred to covers a rudimentary eye, which 
although now functionless 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 Europe there occur remains of reptiles 
Allied Families. . . .. . TT 
allied to the tuatera, but constituting a distinct family ( Homceosaur- 
idee ) typically represented by the genus 
Homoeosaurus. 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 inter¬ 
centra between the vertebrae of the back, 
and no hook-like processes to the ribs. A 
third family ( Rhynchosauridce ) is typified 
by the genus Rhynchosaurus, from the Trias 
or New Red Sandstone of England, and is 
characterised 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 
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. 
The Permian rocks of Europe yield remains of genera, such as 
Oldest Types. , x f ® 
Froterosaurns and Pcdceohattena, differing markedly from the fore¬ 
going, and constituting a second suborder (Proterosauria), characterised by the 
complex nature of the bones forming the shield on the lower surface of the body, 
by the fifth metatarsal bone of the hind-foot being of an ordinary type, and like¬ 
wise by the lower bones of the pelvis being expanded into large flattened plates, 
instead of comparatively narrow. The last feature allies the group to the earlier 
Sauropterygians. In the genus first named the vertebrae of the neck have cup¬ 
shaped articular surfaces behind and balls in front, and there are no intercentra 
between the vertebrae of the back, but in the other the articular surfaces of the 
skull of the Hyperodapedon (J nat. 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. 
