Late adult, equal to usual maximum length, Growth Stage 5f, on Laminaria frond. Shell is a high conoid, steeper at the anterior, resembling a Phrygian cap. It is a rare form as it is easily swept off the frond, so is usually found only in very sheltered conditions or at depth below strong wave action. The posterior is a long smooth convex curve; the anterior is a shorter and steeper concave curve with a break of slope where juvenile growth meets adult growth (1), and, on two year old individuals, where first year adult growth meets second year growth (2).
3: limit of juvenile growth at posterior.
4: point where first year adult growth meets second year growth.
The wide skirt of adult growth all around shell makes up the majority of it. Posterior growth still exceeds anterior growth, but less markedly. The growth lines are continuous around the whole shell on the adult skirt (5) .
The aperture outline is almost circlular, and the rim is on a single plane conforming to the flat surface of a Laminaria frond (6). Interior is blackish with some iridescence (7) , but the shell, thinner than those in holdfasts, is still slightly translucent. Live GS5f shells are usually dark brown. Bright blue rays persist on the juvenile growth and may continue on adult growth for part or all of the way to the posterior edge; on this specimen on the first year of adult growth (8), but not the second year growth (9).

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.