DEFENSIVE ARMOR, SPINES, ETC. 103 



is very certain and frequently observed that our black- 

 snake and otliers which are non-venomous will attack 

 and destroy the rattlesnake. The superiority in this 

 case has usually been attributed to quickness and 

 strength preventing the rattler from striking; but 

 the safety may possibly consist in the scales acting 

 as an armor. Certain it is that the poison -fang is not 

 usually a weapon for fighting a rival, but it is said, 

 however, that n on -poisonous snakes die of the bite 

 of sea-snakes. The question can scarcely be said to 

 be settled yet. 



Defensive Armor, Spines, etc. 



The most striking armor now found in Nature is 

 that of so-called box-turtles where every part of the 

 body is protected. That of the armadillos is almost 

 as good, however. The shells of all tortoise-forms 

 are not so complete as these, and may consist (in a 

 low form) of a mere cap over the body and a mere 

 cross or strip of shell on the bottom. The soft- 

 shelled or leathery sort of turtles have the outer 

 covering above skinny, leathery, or gristly. But in 

 all there is a layer of bones beneath which " breaks 

 joints " in a rough way with the usual array of horny 

 scutes outside. Likewise in many lizards there are 

 flat bones on the back beneath the skin. 



While no ancient reptile had just any such armor 

 as this, we may see that many were rich in bony plates 

 and spines which were very effective. A hint of this 

 remains in the crocodilians. Here there are thick 

 liorny plates placed edge to edge, so strong that they 

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