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DescriptionPatella depressa is distinguished from Patella vulgata by its smaller, flatter shell. The outer surface of the shell is greyish, the inner surface yellowish-white with brown marginal rays. The foot is olive to dark grey (almost black), on tentacles around the edge of mantle white. Apex of the shell anterior. Shell length up to 3 cm long.Patella depressa is notable for not having spread to Ireland from Britain, almost certainly because the distance across St. George's channel is too great for larval dispersal. Seawater warming as a result of climate change is likely to result in northward migration of distribution.