to the ribs in number and extending down over the sides in broad curves so that the animal was completely closed in a bony cuirass. Add to this that the top of the head was heavy and solid, and we can imagine that the animal when it crouched close to the ground, with its head drawn down and in, resembled very closely the modern Armadillo in its attitude of defense and was able to resist the attack of even the long tusked Dimetrodon.
This donning of armor is one of the striking things about the animals of the Permian age; it occurred among the amphibians as well as among the reptiles and is closely correlated with the development of great tusks in the predatory forms. As the armor-piercing weapons grew ever stronger the armor grew ever heavier and more completely adapted to the body. The same thing has happened once and again in the world's history; much later, in Tertiary time, when the world was thirty millions of years older, we have a repetition of the same thing. The great saber-toothed tiger developed canine tusks six inches in length, and the small edentates, the natural prey of the tiger, developed first small isolated bones in the skin, but ever as the tusks grew the bones in the skin became larger and better arranged, until the almost perfect protection of the Armadillo appeared. It was the prophecy of modern warfare between armor-piercing shells and armor plate, we have not seen the end in human history, but in the old days it continued to the practical extinction of both parties to the contest. Perhaps there is a neglected object-lesson here.
Turning from the reptiles to the amphibians, we find a no less wonderful group of animals. During the preceding age, the Carboniferous, the amphibians had been masters of the world; by the Permian, their time of dominance was past and they were already on the downward path that was to end in the obscure toads, frogs and salamanders of our meadows. But they were far from yielding tamely to their fate; they developed in all? possible directions in a seemingly frantic effort to regain their lost dominance. During the Permian and the succeeding Triassic ages, there lived some of the largest amphibians the world has ever seen; they betook themselves to the water and developed eel-like bodies; they lived in hollow trees, as witness the discoveries of Sir Wm. Dawson in the stumps of trees