sentences:  Located among the spines are several types of pedicellaria, moveable stalked structures with jaws.Sea urchins move by walking using their many flexible tube feet in a similar way to starfish; regular sea urchins do not have any favourite walking direction.The tube feet protrude through pairs of pores in the test, and are operated by a water vascular system; this works through hydraulic pressure, allowing the sea urchin to pump water into and out of the tube feet.