Chain corals (Halysites) are an extinct genus of corals, living in warm and shallow seas during the Ordovician and Silurian periods, some 400 to 450 million years ago. They belong to the order of the tabulate corals (Tabulata) and are made of oval, laterally compressed units (corallites) that are connected in chainlike structures. The chains form colonies that range in size from a few to tens of centimeters. The sample here displayed is from glacial debris in moraine deposits accumulated during the Pleistocene Ice Ages in the north Netherlands. The boulders and coarse debris in these deposits are mostly derived from Paleozoic rocks in Scandinavia. Actual width is 120 mm