PLANT-EATING MAMMALS 



179 



almost invariable number of seven, characteristic of Mammals 

 generally, and this flexibility must be of use in enabling the 

 animal to reach a large number of leaves without altering the 

 position of its body. The long mobile tongue is used in pre- 

 hension, and is not unlike the same 

 organ in the related Ant -Eaters, 

 though they, as we have seen, use it 

 in a very different way. As might be 

 anticipated, the teeth are specialized in 

 accordance with the nature of the food, 

 incisors and canines 

 being entirely absent, 

 while the cheek-teeth, 



Fig. 425. — Three-toed Sloth {Bradypus tridactylus) 



of which five are present on each side above and four on each 

 side below, are all or mostly of the nature of blunt-crowned 

 grinders, consisting of dentine covered by a thick coating of 

 enamel. The qualification as to form is rendered necessary by 

 the fact that in the Two-toed Sloth {Ckolcspus) the first cheek- 

 tooth on either side of each jaw is tusk-shaped. The teeth so 



