t and best developed animals in this early Palaeozoic
time. These creatures had bodies jointed like the tail of a lobster.
They were wide and flat, instead of narrow and rounded like a lobster,
and each joint of the body was highest in the middle and distinctly
lower at the two sides, thus forming three regions along their backs.
This structure gives to these creatures the name of trilobites. These
animals were the kings of the early ocean. They had an interesting
habit of curling up nose to tail before they died, and, as a result, a
large proportion of all the trilobite fossils we find are curled in
this peculiar manner.

After these forms the most abundant fossils we find in Silurian times
were creatures that at first sight looked as if they might be related
to the clams. These are known as lampshells, because one shell
projects beyond the other and curls up at the tip so as to resemble
the clay lamps which are dug out of old Roman towns. The lampshells
also have nearly disappeared in modern times. Simple creatures
belonging with our present crab and snail had begun to make their
appearance, but they were not as abundant as we find them later on.

The third group of the mollusks to which the nautilus and squid of
to-day belong is very abundantly represented in the Silurian by
fossils with coiled-up shells. As for the plant life of the time, it
is exceedingly 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 Palaeozoic is known as the Devonian age, or the
age of fishes. Now the backboned 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