RUGOSA (Ordovician through Silurian)

    Also 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.