INTRODUCTION x^ 



tiles to-day. And in support of the reasonableness 

 of this latter view we may appeal to the evidence 

 which the rocks have preserved for us in the shape of 

 the fossil remains of ancestral birds. In these we 

 have still further and more striking proof of the 

 descent of birds from reptiles, and the gradual change 

 from the reptile to the bird type. 



The earliest fossil bird yet discovered is that known 

 as Archaeopteryx, and this differed from all other 

 birds in one or two very important particulars. In 

 each case these differences serve to bridge the gap be- 

 tween the reptiles and the birds, though it must be 

 admitted many other links are necessary to make the 

 chain complete. In the first place, instead of the 

 horny sheaths which cover the beak of living birds, 

 we find the jaws were provided with teeth, set in 

 sockets like those of the crocodile; in the second, the 

 tail was of great length and made up of a long row 

 of bones, as in the tail of reptiles. Each bone sup- 

 ported a pair of feathers, as may be seen in our illus- 

 tration, so that in this respect it was neither like that 

 of the reptile nor of the typical bird. In the latter, 

 the tail is apparently fashioned after a very different 

 manner. 



When we come to examine the arrangement of the 

 tail-feathers in a bird, we find that they are set fan- 

 wise about a plate of bone, the last of a series of the 

 eight separate tail-bones which form the termination 

 of the backbone. But it must be remembered that 

 what is commonly called the "tail" is really only the 

 outward sign of this appendage, for feathers, alone, 



