250 SNAKES, TURTLES, LIZARDS, CROCODILES 



scales on the ventral side of the body are large and extend 

 transversely across the width of the body. These scales 

 are known as scutes. Each scute is attached to a pair of 

 ribs and, moreover, is fastened, or hinged at its anterior 

 edge, while the remaining portion of the scale is free. The 

 scutes are the main organs of locomotion. The free edges 

 of the scutes are brought forward and downward, where 

 they catch against the irregularities of the surface, and 

 when forcibly returned to their normal positions close to 

 the ventral side of the abdomen, force the body forward. 

 If an individual should be placed on a smooth surface, 

 like glass, it would be imable to crawl because no inequali- 

 ties of surface would be presented for the scales to push 

 against. 



The eyes of the garter snakes have no Uds, but are pro- 

 tected by the skin that passes over them, which is trans- 

 parent and somewhat thickened just over the eyes. The 

 absence of eyelids accounts for the cold, stony stare of 

 snakes. No external ear is present. In fact, no snakes 

 have external ears. 



The tongue is forked, and the two halves of the lower jaw 

 are loosely united in front, while the whole jaw is loosely 

 hinged to the head by means of an intermediate bone, the 

 quadrate. This arrangement allows the mouth to be greatly 

 dilated for swallowing its prey. The teeth all point back- 

 ward and are for the purpose of holding its prey, and not 

 for chewing, because the food is swallowed whole. 



Pythons. — It is said that some pythons reach the ex- 

 treme length of thirty feet, but probably twenty feet is 

 nearer the average. They are found in the tropical portions 

 of Asia, Africa, and Australia. A python has a prehensile 

 tail, and by means of this, cUngs to the branches of trees, 



