270 AN INTRODUCTION TO ZOOLOGY. 



not often, met with. The common English Snake, 

 called the Grass Snake, Tropidonotus (or Coluber) 

 Natrix, is quite harmless; it is sometimes called the 

 Ringed Snake, from its collared appearance, due to 

 the presence of a pair of pale spots, followed by a 

 contrasting dark area at the back of the head. 



The Saurii include the Chameleons, Iguanas, and 

 Lizards, and the Crocodiles, besides a number of ex- 

 tinct forms. Some of the latter resemble fishes in 

 having amphicoelous, that is to say, biconcave, verte- 

 bra. The Crocodiles have vertebrae that are concave 

 in front (procoelous), while some extinct kinds had 

 vertebrae concave behind (opisthocoelous). The living 

 Crocodiles include the true Crocodile of the Nile, the 

 Alligators of America, and the Gavials, or Indian 

 crocodiles. 



A few of the Lizards resemble snakes in outward 

 appearance ; among these is the English Slow-worm, 

 or Blind- worm {Anguis fragilis), which sometimes is a 

 cause of fright to those who dislike snakes, but is 

 quite harmless. The little Lizards which . may be 

 found on sunny banks are the only other English 

 representatives of the Saurii; we have two kinds, the 

 Scaly Lizard, Zootoca vivipara ; and the Sand Lizard, 

 Laceria agilis; and a third, L. viridis, is found in 

 Jersey. 



