Tlie Coining of Vertebrates and Rise of Fislies 



Lower Silurian epoch, but a little higher up in 

 the rocks remains of fishlike creatures are met 

 with in abundance ; at least they are abundant 

 in some favored localities, and occasionally so 

 complete and well-preserved that we can get a 

 pretty good idea of their appearance when in 

 the flesh. 



The best known of these fishes have been 

 described over and over again, but while we 

 are not quite so restricted here as with birds 

 — where we have but two individuals to fonn 

 the starting-point for the entire race — yet if 

 we are to obtain an idea of what the early ver- 

 tebrates looked like, it will be necessary to 

 describe them once more. They were small, 

 they had no true back-bone — only a rod of 

 gristle — no skull and no jaws even, for jaws and 

 mouths do not, as might readily be supposed, 

 necessarily go together. But most of them 

 were well protected above and below by bony 

 armor, and as armor implies attack and defense, 

 it is to be inferred that the more powei^l 

 creatures preyed upon the weaker then even as 

 they do now, and those that could not defend 

 7 89 



