LIFE IN THE PAST 173 
ingly difficult to say much about it. There must have 
been nothing but marine plants, and these must have 
been on the general line of the seaweeds. Little can 
be definitely said concerning them. 
The next period of the Paleozoic is known as the 
Devonian age, or the age of fishes. Now the back- 
boned animals first make their clear and unmistakable 
appearance. There are remains in the Silurian which 
show that there must have been a few fishes at that 
time. The Devonian is so full of them and they are 
so well developed and so diversified that this period 
is definitely known as the “age of fishes.” They do 
not closely resemble the fishes of to-day, but anyone 
would recognize most of them for what they are. 
Their bodies were covered, not so much with scales as 
with heavy plates, often arranged like tiles, those on 
the forward half of the animal being often larger 
than those surrounding the rest of the body. The 
creature was encased, as it were, in armor. These 
were the rulers of the Devonian seas. The land, as 
yet, was probably nearly without animal life, the 
creatures thus far being’ almost confined to the water. 
A few insects make their appearance and a few thou- 
sand-leggers are running around among the lowly 
plants; a few spider-like animals have arisen; there 
are a few snails that have left the water and taken 
to the land. Altogether only the dawn of a land 
