MAIL-CLAD ANIMALS. 13 



common parlance these animals are, indeed, very 

 generally termed quadrupeds ; but this name is objec- 

 tionable, in that it is equally applicable to many rep- 

 tiles, and also since it can scarcely be applied to whales, 

 which, as is well known, belong to the same class as 

 man. The term Mammals is, however, becoming some- 

 what popularised in the sense of the older term quadru- 

 peds, and, since it is in every way an excellent one, we 

 shall take leave to employ it. Now, with the exception 

 of one peculiar group or order, all mammals agree with 

 birds in being conspicuous for the absence of a bony 

 bodily armour ; and since they have not the peculiar 

 means of protection possessed by so many of the latter 

 class, they afford striking examples of our thesis that 

 as animals have progressed in organisation they have 

 discarded protection by plates of bone, to find a better 

 one in the strength or speed of their limbs, or in 

 the sharpness of their teeth and talons. 



The solitary group of mammals which has sought 

 protection in a coat-of-mail is the one which comprises 

 the sloths, ant-eaters, and armadillos. Only a few, 

 however, of these creatures have thus protected them- 

 selves ; while some, like the sloths, have sought refuge 

 in an arboreal life ; and others again, like the ant-eaters, 

 have found protection by burrowing in the ground. 

 These mammals, which are scientifically known as the 

 Edentates, are all 6f a very low type of organisation, 

 and widely different from all other members of the 

 class. It is, however; noteworthy that low as they 

 undoubtedly are, yet that they exhibit no signs of 



