260 The Study of Animal Life part hi 



their origin from feverish saurians which acquired the power of 

 flight, and it is also possible that some, perhaps pathological, 

 mother reptile, overflowing in the milk of animal kindness, and 

 retaining her young for a long time within her womb, was the fore- 

 runner of the mammalian race. 



While there are many orders of extinct reptiles — Ichthyosaurs, 

 Plesiosaurs, Deinosaurs, Pterosaurs, and other saurians not yet 

 classified with certainty — the living forms belong to four sets — the 

 lizards, the snakes, the tortoises, and the crocodiles — to which a 

 fifth order should perhaps be added for the New Zealand " lizard " 

 Hatteria or Sphenodon, which is in several respects a living fossil. 



The Lizards (Lacertilia). — The lizards form a central order of 

 Reptiles, but the members are a motley crowd, varied in detailed 

 structure and habit. Usually active in their movements, though 

 fond, too, of lying passive in the sunshine, they are often veiy 

 beautiful in form and colour, and not uncommonly change their 

 tints in sympathetic response to their surroundings. Most lay eggs, 

 but in some, e.g. the common British lizard (Lacerta or Zootoca 

 vivipara), and the slow-worm, the young are hatched within the 

 mother. 



Among the remarkable forms are the Geckos, which with 

 plaited adhesive feet can climb up smooth walls ; the large Monitors 

 ( Varanus), which may attain a length of 6 feet, and prey upon 

 small mammals, birds, frogs, fishes, and eggs ; the poisonous 

 Mexican lizard (Heloderma horridum), with large venom-glands 

 and somewhat fang -like teeth; the worm-like, limbless Amphis- 

 bccna ; the likewise snake-like slow-worm (Anguis fragilis), which 

 well illustrates the tendency lizards have to break in the spasms of 

 capture ; the large Iguanas, which frequent tropical American 

 forests, and feed on leaves and fruit ; the sluggish and spiny 

 "Horned Toad" (Phrynosoma) ; the Agamas of the Old World 

 comparable to the Iguanas of the New ; the Hying Dragon (Draco 

 volans), which, with skin outstretched on extended ribs, swoops 

 from tree to tree; the Australian frilled lizards (Chlamydosaurus) 

 and the quaint thorny Moloch ; the single marine lizard (Oto- 

 cephalus or Amblyrhynchus cristatus) from the Galapagos ; and the 

 divergent Chamseleons, flushing with changeful colour. 



The New Zealand Hatteria or Sphenodon is quite unique, and 

 seems to be the sole survivor of an extinct order — Rhynchocephalia. 

 It was in it first of all that the pineal body — an upgrowth from the 

 mid-brain of backboned animals — was seen to be a degenerate 

 upward-looking eye. 



Snakes or Serpents (Ophidia). — These much modified 

 reptiles mostly cleave to the earth, though there are among them 

 clever climbers, swift swimmers, and powerful burrowers. Though 



