184 FIRST LESSONS IN ZOOLOGY. 



thus we see that the lizard, on the whole, is much more like 

 a bird than a salamander. The lizard lives a more active 

 life than the salamander, and we shall see that certain forms 

 now extinct fairly rivalled the birds in power of flight. 

 Reptiles are vastly more numerous in species than amphib- 

 ians, and play a more important part in the animal econ- 

 omy. 



As a general rule, then, the lizard and other reptiles are 

 air-breathers, with scaly bodies, their limbs ending in 

 claws ; their ribs tvell developed, their eyes ivith two lids, 

 their nose with nostrils ; the circulation of the blood is 

 incomjiletely double, and the eggs are large. They do not 

 pass through a met amor 2)ho sis. 



ORDERS OF LIVING REPTILES. 



1. Body long, slender, cylindrical, 



limbless Ophidia. Snakes. 



2. Body with a long tail; usually two 



pairs of limbs Lacertilia. Lizards. 



3. Body inclosed in a thick shell .... Chelonia. Turtles. 



4. Lizard-like; vertebrae hollow at 



each end Rhync?iocep7ialm. Sphenodon. 



5. Body thick scaled; teeth in sockets. Orocodilia. Crocodiles. 



The Lizards. Let us now look at lizards more in gen- 

 eral, and afterwards we can learn in how many ways the 

 various kinds are adapted to different modes of life. Most 

 lizards have cylindrical bodies, usually covered with small 

 overlapping scales, with a long, slender tail, and generally 

 two pairs of feet, the toes long and slender, and ending in 

 claws. They run with great rapidity, and are active, agile 

 creatures, adorned with bright metallic colors, in some 

 cases green or brown, simulating the tints of the vegetation 

 or soil on which they live ; some are capable of changing 

 their color at will, as the chameleon and Anolis ; this is 

 due to the fact that the pigment- or color-cells are under 

 the influence of the creature's will. 



In many lizards (Lacerta, Iguana, and the Geckos) the 



