Biology/Natural History: Acmaea mitra is known by its tall shell, which can reach a height of 30 mm and a length of 35 mm. The scientific name means "pointed cap". This species eats coralline aglae using its radula. The teeth of its radula are unique amoung marine invertebrates, as they are capped with goethite, and also with silica (opal). Goethite is an iron compound that forms a hard crystalline cap around the teeth. A. mitra is also fairly unique amoung limpets as it does not appear to have any defense response system to predators. Predators include the seastar Orthasterias koehleri and birds such as black oystercatchers and white-winged scoters.