Single specimen, 8 mm diameter, with rounded kite-shape aperture which can be mistaken for C. montagui, surrounded by smaller C. montagui. On live Patella vulgata.
Portland Bill, Dorset. April 2012.
Masses of Chthamalus near high water mark on shores exposed to strong waves are a favoured habitat of the isopod Campocea hirsuta ( 1) and juveniles of the gastropod Melarhaphe neritoides (2).