Left: the wide black-lichen/splash zone, between white barnacle zone below and orange lichen zone above, on exposed headland rocks with many crevices for moisture and shelter from waves, is the ideal habitat for M. neritoides.
The black zone narrows as exposure/splash decrease away from the tip of the headland. Lleyn Peninsula, Wales on a calm day.
Right: the spray and swash zone at high water is very wide on the exposed tip of Portland Bill, Dorset, where millions of M. neritoides live. © A. Knowles.