Coral Rag

Coral Rag, or Corallian stage, so named from the abundance of its fossil corals, is one of the most distinctive subdivisions of the Jurassic system, being traceable from the Mediterranean to Normandy and right across England from Weymouth to Filey. It varies much in thickness, occurring, in fact, in lenticular masses, and consists in England of rubbly limestone, true coral-reefs, grits, and clays, and of massive limestones in Switzerland, Germany, and France. In addition to such corals as Thecosmilia, Thamnastraea, and Isastraea, the most characteristic fossil is he urchin Cidaris florigemma. Oolitic limonite (hydrous oxide of iron) is worked in the Corallian at Abbotsbury, near Weymouth; and at Headington, near Oxford, a limestone in the series is much quarried for building.