Large Polished Fossil Goniatite Devonian Period, 417-354 million years B.P. A large free-standing Sporadoceras sp. goniatite, polished through the shell to reveal the calcite preserved inside and showing the dividing gas chambers, known as suture patterns, where the chambers meet the surface revealing a zigzag pattern. 922 grams, 16 cm (6 1/4 in.). From a Cambridgeshire, UK, collection. [No Reserve]