GRASS SNAKE. 



147 



upper jaw, and is only " erected" when the Snake is prepared 

 to strike. 



Externally the Snake is covered by small overlapping scales 



1 ir 



The Head Shields of a Snake. 



r, rostral shield ; ff, anterior and posterior frontal ; v, interparietal ; s, snpraocular ; 

 <?, parietal ; nn', nasal ; /, loreal ; a, preocular ; /, postocular ; un, upper 

 labial ; //', temporal ; /;/, mental ; ** } lower labial ; cc, chin-shields. After 

 Giinther. 



on the upper parts and by broad plates on the under surface. 

 The head is covered mainly by shields, each of which has a 



