ON THE PEDIGREE OF THE CORAL-REEFS OF ENGLAND. 199 
Creracrtous CoRALs. 
We will very briefly refer to these. In the English chalk 
there are several small corals, mostly of single growth. In 
the sandy commons between the Great Western line and the 
town of Faringdon, in Berkshire, there are very numerous 
small excavations, which disclose beds of exquisite sponges 
and Polyzoa, but no corals. On the summit of Haldon, in 
South Devon, are remains of a small coral-reef in the Lower 
Greensand. 
There are seventy-six species of corals enumerated from the 
Cretaceous strata, not reef-builders. 
TrrTIARY CoRAZs. 
Still higher up, or more recent, in the early part of the 
Tertiary period, vast coral-reefs are found, of which the re- 
mains are now visible in Central and Southern Hurope, in 
Egypt, Syria, Arabia, and parts of India. In our own island 
we find in the Suffolk Crag numerous beautiful Polyzoa, some 
sponges, and but very few corals, and those only of the single 
kinds. 
Now, having given a cursory sketch of the dwelling-places, 
we must glance at the dwellers. 
The coral-animal may be described as a tiny sea-anemone, 
which secretes within itself a stony cell having upright par- 
titions. The building rises up as it grows, and when the 
creature dies, the little cell and its ribs become visible. In 
one group of corals, called tabulate corals, there are horizontal 
plates as well as vertical; in the other there are vertical plates 
only. The latter group is called Rugose, or wrinkled corals. 
_ The little Polyps (as the animals are called), are of several 
kinds; many haveatendency to live together in colonies. In 
the live coral we find only a smal! bag of animated substance 
open at the top, but more or less closed at the lower end. The 
inside of this bag has the power or property, by vital 
chemistry, of extricating and fixing grains of carbonate of 
lime from sea-water. 
The reef-corals comprise :— 
. All the Star-corals (Astreide). 
. All the Mushroom-corals (Fungacie). 
. Certain of the Eye-corals (Oculinide). 
CoD 
