3 I2 



ELEMENTARY ZOOLOGY. 



(see Fig. 122). This enables them to swallow living ob- 

 jects much larger than the body itself. There are several 

 species of snakes that are poisonous, and this fact has 

 given the whole group a bad name which they do not 

 deserve. The poison gland is one of the salivary glands 

 modified; and the poison fang is a modified tooth. The 

 chief poisonous types are the vipers of Europe, the cobra 

 of the East Indies, the rattlesnake, the copperhead, and 

 the water-moccasin of our own country. 



FIG. 127. Common box- tortoise (Cistudo Carolina). Photo by Shufeldt. 



The pythons, the boa, acid the anaconda capture and 

 crush their prey by the muscular fold of the body. These 

 are the giants of the orde^r. Other common types are 

 the green-grass snake, the garter-snake, the water-snakes, 

 and the black-snake. These are not poisonous. 



The turtles (Chelonia, Fig. 127) have short, wide bodies 

 which may be flat or much arched. There are two pro- 

 tective cases the arched carapace above, and the flattened 



