THE TORTOISES 



THE TORTOISES (Family TesTUDINID^) 



Most of us have seen a Tortoise, and have wondered at its 

 hard, horny shell, its small, weak legs, and the odd little head 

 which it can draw back quite out of sight into its shell. 



A number of tortoises may sometimes be seen for sale upon 

 a truck in the street. These have probably just been brought 



Tortoise 



over here in some ship. For in certain countries they are so 

 extremely plentiful that they are actually collected and put into 

 ships to serve as ballast! 



Now, the shell of a tortoise is not a covering, like that of a 

 snail or a periwinkle. Properly speaking, indeed, we ought not 

 to call it a "shell" at all; for it is externally made of horn, and 

 internally of what in mammals are parts of their bony skeleton. 

 Strange as it may seem, the upper part consists of the ribs, and 

 the lower part of the breast-bone! These grow on the outside 

 instead of inside the body, and are greatly widened out and 

 flattened. If the upper shell is taken off, the course of the ribs 

 may be traced on its under surface. The ribs are covered with 



