XXIV. REPTILES 



The Spotted or Mud Turtle (Chelopus guttatus) . — For a classroom exercise 

 use living turtles. The body is flattened, and is covered on the dorsal and 

 ventral sides by a bony framework. This covering is composed of plates 

 cemented to the true bone underneath, the whole forming one horny cover. 

 What is the general arrangement of these plates ? The dorsal covering is 

 known as the carapace, the ventral one the plastron, the connection between 

 them the bridge. Allow the animal to remain quiet for a moment, then 

 touch the head suddenly. What is one function of the shell? In the box 

 turtle this adaptation is made more evident by a hinge in the plastron 

 which fits over the head and legs after they are withdrawn into the shell. 



Adaptations. — Place a lively turtle on its back. How does it attempt 

 to regain equilibrium ? Notice the long neck. The long neck and powerful 

 horny jaws are of great use to the animal in food getting. Allow the 

 turtle to crawl on the table. Then place it in a dish of water. How are 

 the legs adapted to movement in the water ? How is the foot adapted for 

 other purposes ? 



Turtles are very strong for their size. The stout legs carry the animal 

 slowly on land, and in the water, being slightly webbed, they are of service 

 in swimming. The strong claws are used for digging especially at egg-lay- 

 ing season, for some forms of turtles dig large holes in sandy beaches in 

 which the eggs are deposited. 



Watch a turtle feeding. Notice that the claws are used. How? The 

 absence of teeth makes it necessary for the turtle to tear the food with 



the aid of the strong claws. 



The sense of hearing in the turtles is not keen. 

 The tympanic membrane can be seen just behind 

 the eyes on the sides of the head. Can you deter- 

 mine by experiment anything regarding keenness 

 of vision in the turtle ? Is the turtle protectively 

 colored? Describe any evidences you may see. 

 Notice that the yellow, ventral side would har- 

 monize the general coloring, looking through the 

 water toward the surface of the pond. The yellow 

 dots on the black background look in the water 

 much like small stones or sand grains. 



Draw the turtle, natural size, from the dorsal 

 Western painted turtle. side and label all the parts you know. 



The Turtles. — The turtles form a large and interesting group 

 of animals. They are mostly aquatic in habit. Some exceptions 

 are found, however, as in the case of the box tortoise {Cistudo 

 Carolina) and the giant tortoise of the Galapagos Islands. This 

 latter animal attains a weight of three hundred pounds or more 

 and may be over four feet in length and almost three feet in 



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