THE TRANSITION TO LAND 



385 



they have been able to survive while their more active relatives became 

 extinct. Although amphibians typically have a smooth skin, the reptiles 

 have scales on their bodies. In this group of reptiles some of the scales 

 have become greatly enlarged, thickened, and fused together to form the 

 "shell." In many turtles this is hinged so that the head and legs may 

 be drawn inside and the "shell" tightly closed. Land turtles are usually 

 referred to as tortoises, while the name turtle is commonly used when re- 

 ferring to those that live primarily in the water. Turtles hold the 

 world's record for holding their breath under water, for they have been 

 known to stay submerged for as long as three hours without coming up 

 for air. 



Photo by Winchester 



Fig. 26.7. Galapagos tortoises. These huge reptiles, living on the Galapagos islands, 

 where enemies are few, often live to be several hundred years of age. This group is 



kept at the Brookfield Zoo in Chicago. 



On the Galapagos Islands there are huge tortoises weighing several 

 hundred pounds and estimated to be up to four hundred years old. They 

 are probably the oldest living animals on the earth. 



Crocodiles and Alligators. These are the giants of the living rep- 

 tiles ; they frequently grow to a length of twenty feet and have actually 

 been measured thirty feet long. Their huge bodies, armed with power- 

 ful jaws lined with sharp teeth, make the crocodiles antagonists to be re- 

 spected by any living creature. They are always found in or near large 

 bodies of water. They may often be seen sleeping on the bank of a 

 tropical river, but on being disturbed they plunge into the water where 

 they are undisputed masters. At other times they float lazily near the 

 surface, with just their nostrils, eyes, and the upper parts of their heads 

 above the water. In this position they look very much like floating logs. 



There are only slight differences in the crocodiles and alligators, but 

 the crocodile seems to be the more vicious and aggressive of the two. 



