RUGOSA (Ordovician through Silurian)
known as tetra corals, horn corals or cup corals, the rugosans are usually
large. they me be found in a colonial mass or solitary and are readily
fossilized. They have the basic shape of an inverted cone and well
developed radial septa. Long septa usually alternate short ones.
The walls of the corallites (one single coral organism) are either composed
from the thickened bases of the septa or arched plates inclined towards
the center of the cone. Solitary rugose coral may be found curved
or erect, short or tall and wide or tightly cylindrical. Rugosans
can be closely packed or only attached by horizontal tubes.