Same as Fig. 28 but showing the frustum containing the horns. Darker shading indicates increased surface brightness of an echo. (a) The complete frustum as revealed through a complete, regularly sampled set of echoes. Random points along the intersection of the frustum with echo parabolae from our observations are shown in panels (b) (face‐on) and (c) (from the top). Gray scale is normalized to the brightest and faintest points plotted, thus shadings differ between panels (a) and (b)–(c).