REPTILES. 201 



Glass Snake of this country is also one of the same kind 

 of Snake Lizards. 



330. In the family of Naked-eyed Lizards the approach 

 to the Serpents is still greater. Not only is the body 

 snake-like, but the eyes are, as in the Snakes, destitute 

 of eyelids, and covered only with a transparent portion 

 of the skin. Most of the species of this family are na- 

 tives of Australia, and only one is found in America. 



331. We now come to the order of Snakes or Serpents. 

 The grand peculiarities of this order are the total ab- 

 sence of limbs, the great flexibility of the chain of verte- 

 brae, which runs through the whole length of the animal, 

 and the covering of scales. Over the scales spreads very 

 closely a thin delicate skin, which is shed every year or 

 oftener, a new one forming in its place. The separation 

 is begun at the head, and the skin, in being cast off, is 

 turned inside out, as we sometimes turn the finger of a 

 glove. The Serpents of temperate climates hibernate, 

 and on waking up in the spring cast off their skins. 



332. The skeleton of a serpent is very simple, consist- 

 ing only of the skull, the column of vertebra, and the 

 ribs. There is no breast-bone. Each vertebra is united 

 by a ball and socket joint with the one next to it. It is 

 this arrangement that enables the animal to execute its 

 free and graceful movements. The vertebraB, in some 

 cases, number as high .as three hundred. 



333. The ordinary forward movement of the Serpent 

 is made by the ribs, the scale which is at the end of each 

 one of them acting as a foot on the ground. These scales 

 being successively pushed backward against the earth, 

 the annual is moved forward. But sometimes it gathers 

 itself up into a coil, and then, by the sudden straighten- 

 ing out of its whole body, it can at once reach more than 

 its whole length, leaping upon its prey. 



334. The senses of the Serpents are not highly devel- 

 oped. Sight is the most perfect of all its senses. The 

 eyes, however, are small, without eyelids, being covered 



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