FOSSIL ANIMALS 285 



living species of fishes 11,500 belong to the great group 

 of Teleostomi or bony fishes, of which the first representatives 

 are found only in Triassic strata. But fossil fishes are known 

 from all the geologic periods from the Silurian on up. All 

 the fishes of these earlier millions of years were of more 

 primitive shark-like families. Many of these families 

 are now wholly extinct and of the others only a few per- 

 sisting species remain. Even those early families of the 

 true bony fishes of the Triassic and Jurassic rocks are mostly 

 now extinct. Most modern families date from Cretaceous 

 times. 



The question may be asked: Are there any fossil men 

 known? The answer is yes. But man is very young, 

 geologically speaking. No indubitable human bones or 

 relics have been found in rocks earlier than those of the 

 present great epoch, the Quaternary. But this epoch is 

 certainly already many thousand years old. Man existed 

 in Glacial times. Remains of the mammoth, the cave-lion, 

 cave-bear, and other extinct animals have been found in 

 the same caves with human bones. So man has a certain 

 geologic history; one at least of 20,000 years; probably 

 much longer. 



