Limpets at home

While looking for drawings of seashells online, I came across this photo of limpets (from here) -

Those circles are known as "home scars" and they are made over the years as each limpet returns, after grazing in a zig-zag pattern when the tide is in, scraping tiny organisms off the rock with its rasping tongue, to its exact place on the rock. When the tide is out they cling to the rock ... like limpets ...

Patella ferruginea can be 8cm across (via)