Motion pictures were taken of the locomotion of two species of ophiurans living in the Sea of Japan:Ophiura sarsi vadicoa Djakonov andAmphipholis kochii Lutken.Ophiura sarsi was found to move with the aid of paddling movements of two pairs of arms: The fifth arm (passive) pointed backward. Ophiurans of this species do not use their ambulacral feet. Three main types of locomotor movements were distinguished inAmphipholis kochii, First, locomotion by the "breast stroke" method, in which one arm (the leading) points forward, two point to the side, and two backward. The two side arms are periodically carried forward, after which the disk and the remaining arms are moved with their aid. In this method waves of flexion and extension of the segments spread along the side arms. Second, displacement by pulling with the leading arm pushing with the hind arms, and third, movement by stepping movements of the ambulacral feet. These three methods of locomotion can be used either independently or in various combinations with each other. The ambulacral feet also provide the link between the active arms and the supporting surface by means of which the ophiurans can move forward.