#772 - Patelloida alticostata - Tall-ribbed Star Limpet
A genus of limpets distinguished by the large radial ridges, and resultant wavy outline to the shell. Like the more familiar true limpets, harmless algae-scrapers. Also like the True Limpets, possess a single feathery gill.
Cape Peron, Perth
EDIT: Helpfully IDed further by Joan Hales at BowerBird. According to her “A common southern Australian shell attached to rocks from about the half tide level down.  The black lines are a give-away.“









