36 
HAROLD’S DISCUSSIONS. 
seum where they are arranged in the order of the 
ages to which they belong. 
There is very little evidence that either plant or 
animal life existed on the earth dur¬ 
ing the Archaean age. Some geolo¬ 
gists have found what appear to he 
remains of plants; indeed, they are 
quite sure that these are fossils of 
jDlants which existed during that 
period. But when we examine the 
rocks immediately on top of these 
Archaean strata, we soon find fossils 
of both plants and animals. 
The first fossil to attract our at¬ 
tention is a crah-like animal called 
the trilobite. As you may see from 
Fig. 14, it is divided into three lobes 
by two divisions along the back. 
It has a roundish head and rather 
prominent eyes. There are many 
kinds, varying in size from a pea to 
several feet in length. Then, too, 
a little bivalve called the lingula 
seems to have been abundant, as the 
rocks are full of their fossils. Al¬ 
though the trilobite is the most striking form of life 
we meet, it is by no means the earliest, nor was 
the lingula, for long before either of these two ani¬ 
mals made its appearance, the waters evidently 
abounded in smaller protozoan forms. There were 
also animals in the sea water that looked somewhat 
Fig. 15.—Lingula, 
showing stem by 
which it attached 
itself to rocks. 
