BONE BED, a term loosely used by geologists to denote any stratum or deposit which contains bones. It is applied therefore not only to those interstratified layers occurring at definite geological horizons, but also to the brecciated and stalagmitic deposits found on the floors of caves. The stratified deposits are frequently associated with current bedding and prob ably indicate a sorting out and segregation of the heavier bony material accompanying partial or complete removal of the finer sediment by the action of currents. A well known bone bed of this nature, the Ludlow Bone Bed, composed of fragments of spines, teeth and scales of ganoid fish, occurs at the base of the Downton Castle Sandstone in Britain.