Cruziana: A stratigraphically useful trace fossil

Cruziana semiplicata (Salter) is recorded, generally in abundance, from previously known and new localities within Upper Cambrian (Ffestiniog) sediments in Snowdonia, and the Portmadoc area, North Wales. C. furcifera (D'Orb) is recorded for the first time in the British Isles from four localities within Lower Ordovician (Arenig) sediments on St. Tudwal's Peninsula, North Wales. It is shown that each of these species is of limited but different range, and it is suggested that they could be useful in distinguishing between otherwise unfossiliferous Cambrian and Ordovician strata.