PASSIVE DEFENCE 



333 



with defensive plates and spines which oppose considerable re- 

 sistance to attack. 



ARMOURED ANIMALS. Both plate-armour and spiny coverings 

 are found in many groups of the animal kingdom, the former 

 simply warding off teeth and claws, while the latter are calcu- 

 lated to inflict injury upon enemies coming to close quarters. 

 Several orders of Mammals possess arrangements of the kind. 

 Among Edentates, 

 for instance, Arma- 

 dilloes are pro- 

 tected by cuirasses 

 composed of bony 

 plates, and Pango- 

 lins by scale -ar- 

 mour. Among Ro 

 dents, the Porcu- 

 pines are clothed 

 with effective spines (sometimes barbed), as are Hedgehogs among 

 Insectivores, and Spiny Ant- Eaters among Monotremes. 



Birds are provided with scale-armour on their legs, and their 

 feathers constitute a protective coating by which, no doubt, many 



Fig. 490. Diagram of varieties of Reptilian Armour, as seen in section 

 A, Granular scales. B, Flat scales or shields, c, Overlapping scales. D, The 

 same, with underlying bony plates (scutes), ft, Hard outer layer of epidermis; 

 s, deeper layer of epidermis; / ; dermis; <?, bony plates. 



Fig 491. Nile Crocodile. Two scutes, covered by horny epidermal plates. From a photograph 



bites and stings are prevented from taking effect upon the under- 

 lying skin, which is here unusually thin and delicate. Armoured 

 Reptiles are common (fig. 490), Crocodilians (fig. 491) and Chelo- 

 nians (turtles and tortoises) affording the best instances of protec- 

 tive plates, while one of the Australian Lizards (Moloch horridus] 



