2 62 ECONOMIC ZOOLOGY AND ENTOMOLOGY 



Eyes are always present and are highly developed. They 

 resemble the eyes of birds in many particulars. All reptiles, 

 except the snakes and a few lizards, have movable eyelids, 

 including a nictitating membrane like that of the birds. 

 With the snake the eye is protected by the outer skin, a 

 transparent portion of which remains intact over the eye. 

 Turtles and lizards have a ring of bony plates surrounding the 

 eyes similar to that of birds. In addition to the usual eye 

 there is in many lizards a remarkable eye-like organ, the so- 

 called pineal eye, which is situated in the roof of the cranium, 

 and is believed to be the vestige of a true third eye, which in 

 ancient reptiles was probably a well-developed organ. 



Classification. The living reptiles may be divided into four 

 orders. One of these, the order Rhynchocephalia, includes only 

 a single lizard-like genus confined to New Zealand. The 

 Chelonia, including the turtles and tortoises, are distinguished 

 by the scaly, bony or leathery shell covering the body. The 

 Crocodilia, or crocodiles and alligators, have the body covered 

 with rows of sculptured horny scutes or scales, while the 

 lizards and snakes, order Squamata, are usually covered with 

 many small, flat, horny, epidermal scales. 



Turtles and Tortoises. The short stout body of these 

 animals is enclosed in a more or less firm shell, which consists 

 of an upper portion, the carapace, that is firmly joined along 

 the sides to the lower portion, the plastron. From the front 

 opening of this box-like covering the head and forelegs may 

 be protruded when the animal is feeding or moving about, 

 the hind legs and tail being extended from the opening along 

 the posterior margin. When the appendages are withdrawn 

 they fit snugly into these openings and the whole animal is 

 comparatively safe from its enemies. In some turtles the 

 shell does not become hard and horny, but remains soft or 

 leathery. The head usually terminates in a hooked beak and 

 serves as a formidable weapon of offense or defense. Many 

 of the turtles are wholly aquatic, feeding on fish, frogs, worms, 

 molluscs and sometimes small water-fowl or upon the grasses 

 that grow in the water. Others spend a part of their time on 

 the land and part in the water while still others are wholly 



