Fig. 8. Kinematics of the ridge. (A) Plot of the antero-posterior length of the ridge as seen in a top view versus the antero-posterior length of the protrusion of the ridge above a circular arc fitted to the odontophore in a side view (r²=0.84, P<0.002). Fig. 5 shows one frame of these data and how they were analyzed. Lengths are measured in radular stalk width units (RSW). (B) Area of the ridge recorded in vitro during a dopamine-induced series of movements. See Fig. 7B for definitions of events labelled on the x axis. Area is reported in units of RSW². (C) Area of the ridge recorded in vivo from mid-sagittal frames (sequence 7732-S3, frames 16-39). Note the large ridge area at the end of protraction and at the onset of retraction, which corresponds to events 4 and 5 of the in vitro data, i.e. radular closure and odontophore elongation.