VERTEBRATA. 
321 
Fig. 299. — a, Head of a Harmless Snake (upper view); 6, heads of various Venomous 
Snakes. 
pil is round, and the tail tapering. This rule, however, 
has man} 7 exceptions. 
2. Lacertilia , or Lizards, may be likened to Snakes pro¬ 
vided with four limbs, each having five digits. 185 The 
bod} 7 is covered with horny scales. All have teeth, which 
are simple in structure; and the halves of the lower jaw 
are firmly united in front, while those of Snakes are 
Fig. 300.—Lizard ( Lacerta ). 
21 
