Left: dorsal view. Right: ventral view.
Plants, other than Laminaria, that are sometimes occupied, mainly by juveniles, include Alaria, Himanthalia and Fucus serratus. It is uncertain whether these foodplants are adequate for development as adults are only occasionally found on them. They may be those that have failed to reach Laminaria or have been swept off it by storms. The specimen in this image has obviously been displaced as it is the adult form found encased in holdfasts; it can only have been freed by the holdfast being torn from its attachment. It is clearly too wide for the frond of Ascophyllum it is on, leaving it exposed to attack.
Concise
Part 1, SHELL FORMS: 02 Patella pellucida. Growth Stage 2 (GS2). July 2012. Littoral. North Yorkshire, England. © P. Lightfoot.
Part 2, BODY & ANATOMY: 03 Patella pellucida. Growth Stage 3 (GS3). 2009. Sublittoral, Farne Islands, Northumberland, England. © P.Lightfoot.
Part, 3 HABITS & ECOLOGY: 04 Patella pellucida. Length 4.6mm. Growth Stage 3 (GS3). September 2016. Yorkshire, England. © P.Lightfoot.