For a considerable time in the world's history the reptiles were the dominant vertebrate class, and in the chalk period especially they were represented by a great variety of forms, and by a number of species of colossal stature, one at least of which was over a hundred feet long. In those times the reptiles were by no means all condemned to crawl on their bellies, for they included a large number of marine forms, comparable to the porpoises and whales among the mammals, and flying forms whose aspect must have resembled, and been equally terrifying with, that of our mythical dragons. A few reconstructions of these are shown in Fig. 91. [Illustration: Photo: Berridge. FIG. 92.--Reptiles--A Chameleon.] [Illustration: Photo: Berridge. FIG. 93.--Reptiles--Indian Python.] [Illustration: FIG. 94.--Reptiles--Turtle and Tortoises.] [Illustration: FIG. 95.--Reptiles--Alligator.] All living reptiles, with a single exception, belong to the four comparatively modern types of the lizards, snakes, tortoises, and crocodiles, of which examples are illustrated in Figs. 92 to 95. None of these are closely related to the mammals or birds. For the common ancestor of all these types we must go back to some primitive reptile form. Fortunately such a type is represented at the present day in a single peculiar species found in New Zealand, which bears the Maori name of the Tuatara. It was formerly found commonly on the mainland, but is now confined to a few small islands in the Bay of Plenty, North Island, where it enjoys Government protection. It is, as the illustration in Fig. 96 shows, a lizard-like creature, and reaches a length of about two feet. It lives in burrows near the shore, and feeds on small animals that are left behind by the tide. The Sphenodon, as zoologists have named it, has apparently been preserved owing to the absence of competition by the mammals, and by adopting the rather curious mode of life just described. In all its features, but especially in the primitive condition of its vertebræ, it is very much lower than any other living reptile, and it connects the higher groups with the Amphibia. Many closely related fossil species are known, one of which is shown in Fig. 97. [Illustration: FIG. 96.--The Tuatara, _Sphenodon punctatus_.] [Illustration: FIG. 97.--_Homeosaurus pulchellus._ A fossil early reptile from the Jurassic.]