STARFISH 59 
* polyps,” as the animals are called. They are not 
insects, but creatures very much lower in the scale 
of creation. It is natural that corals, which con- 
struct such masses of shells, should have made a 
goodly contribution to the limestone rocks of the 
world. Some of the fossil corals differ greatly 
from the modern reef-building type. The Rugose 
(wrinkled) corals of the Silurian Age built up thick 
and rugged walls, and then there are remains of 
corals which lived as independent individuals, not 
in colonies, but by themselves. Wenlock Edge, in 
Shropshire, is a Silurian coral reef. Fossil corals are 
often found associated with fossil starfish, sea-lilies, 
worms, and other marine animals. This is what 
we should expect, for many marine animals flourish 
on or near coral reefs, and what happens now is 
likely to have happened when the ancient reets 
were in the sea. Various species of fossil corals 
are to be found in the limestones of all Periods from 
the Silurian and upwards. 
But I must push on, and not enlarge too much, 
for I have yet a lot of fossils to tell you about. 
The Ecurnopermata (Greek, echinos=a hedge- 
hog, derma=skin), the creatures which possess 
spinous or thorny skins, form the fourth subdivision 
of the Animal Kingdom. I am sure you will be 
able to think of some of the animals which are 
included in it. What sea-animals have thorny skins ? 
Why, starfishes and sea-urchins, of course ! 
Just a few words about Starfishes. Perhaps the 
best example of these animals is the common five- 
armed starfish, specimens of which you so often see 
at the seaside. You will be familiar with the star- 
