EVIDENCE OF FOSSIL REMAINS 93 



geological horizon until after some sini])le type belong- 

 ing to a class from which it may have taken its origin ; 

 in brief, there are no anachronisms in the record, wliich 

 always corresponds with the record written by com- 

 parative anatomy, wherever the facts enable a compar- 

 ison to be made. 



But the extinct animals of the third and fourth ages 

 are more interesting to us, because there are more of 

 them and because they are more like the well-known 

 organisms of our present era. These two ages are 

 called the Mesozoic or Secondary, and the Cenozoic or 

 Tertiary. The former is so named because it was a 

 transitional age of animals that are intermediate in a 

 general way between the primitive forms of the i)re- 

 ceding age and those of the next period; the latter 

 name means the '^ recent-animal" age, when evolution 

 produced not only the larger groups of our present 

 animal series, but also many of the smaller branches of 

 the genealogical tree Hke orders and families to which 

 the species of to-day belong. 



Confining our attention to the large vertebrate classes, 

 the testimony of the rocks proves, as we have said, tliat 

 fishes appeared first in what are called the Silurian and 

 Devonian epochs, w^here they developed into a ricli 

 and varied array of types unequaled in modern times. 

 At that period, they were the highest existing animals — 

 the '^ lords of creation," as it were. To change the 

 figure, their branch constituted the top of the animal 

 tree of the time, but as other branches grew ujiwards 

 to bear their twigs and leaves, as the counterparts of 

 species, the species of the branch of fishes decreased in 

 number and variety, as do the leaves of a lower part of a 

 tree when higher limbs grow to overshadow them. 



