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INTRODUCTION TO ZOOLOGY. 



the body enclosed between two shields, with apertures for 

 the head, the tail, and the four legs. The jaws are horny 

 and without teeth. 



If we look upon one of the common Land Tortoises, slowly 

 pacing along, and clad in its unyielding armour, we arc 

 inclined to ask, " Why should it be called a vertebrate 

 animal? Where are the vertebrae and the ribs?" 



If we examine the under side of the shield that covers 

 the back of the animal (Fig. 233), the question may with 

 ease be answered. The structure of that shield or, as it is 

 termed, the carapace reveals the vertebrae and ribs, but 



Fig. 233. SKELETON OF TORTOISE.* 



* Fig. 233. SKELETON OF LAND TORTOISE with the plastron or lower shell 

 removed. vc, cervical vertebra; dv, dorsal vertebrae; /-, ribs; sr, sternal ribs, or 

 marginal pieces of the carapace; o, scapula; cl, clavicle; co, coracoid bone; 

 p, pelvis ; /, femur ; t, tibia ; fi, fibula. 



