Sketch of the side view (top) and the ventral foot (bottom) of a terrestrial gastropod showing the location of the waves, interwaves and rim. The animal is moving from left to right. The vertical displacements associated with the pedal waves are not to scale. Vwave, speed of the pedal waves; V, speed of the interwaves; Vslug, overall crawling speed of the animal; Vrim, speed of the rim.