Left: adult Steromphala umbilicalis shell has broad red to reddish-purple bands radiating from the apex across all its whorls. Width 16.4 mm.
Centre: young P. lineatus has zig-zag (1) streaks of dark-brown, -green, -grey or –reddish purple that are only arranged into bands radiating from the apex on early whorls (2). Width 14 mm.
Right: early juvenile P. lineatus misidentified on the basis of view 3 by three very experienced recorders as S. umbilicalis until told that the apertural view with the distinct white tooth (4) and no umbilicus was the same specimen. © R.Durrant.