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, a<^ seen in section 

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

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

 s, deeper layer of epidermis; /, dermis; 0, 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) 



