sentences:  Articulated crinoid fossils are relatively rare, but disarticulated columnals are quite common in the fossil record.They may be extracted from their matrix (often limestone) or, in the case of exposures in coastal cliffs, they can sometimes be found washed out of the matrix and deposited on the foreshore, as if from the sea.In mediaeval Northumberland, the fossilised columnals were collected at Lindisfarne, and strung together as a necklace or rosary.