252 



TYPES OF ANIMAL LIFE 



bones of the neck. Every other mammal besides them 

 with two solitary exceptions has the same number of 

 these bones. Whether the neck is extremely long, as in 

 the giraffe, or extremely short as in the mole, and still 

 more so relatively in the whale, and porpoises, seven 



FIG. 68. 



THE TWO-TOED SLOTH. 



neck-bones and no more are always present. The same 

 is also the case with man. One variety of two-toed 

 sloths has also seven neck-bones, but a closely allied 

 form, called Hoffman's sloth, has only six. This latter is 

 the more northern kind of unau, and it extends from 

 Ecuador, through Panama, to Co.sta Rica. 



The other genus of sloths contains the " ai," or 



