45 Patella pellucida. Growth Stages 3 (top left) & 4 (GS3 & 4) on Laminaria hyperborea frond. October 2013. Sublittoral. Egersund, S. Norway. © E. Svensen.

45 Patella pellucida. Growth Stages 3 (top left) & 4 (GS3 & 4) on Laminaria hyperborea frond.  October 2013. Sublittoral. Egersund, S. Norway. © E. Svensen.

Most early adults (GS4) on fronds in Norway differ from those in Britain as blue lines usually continue onto new adult growth at the anterior in Norway (1) but not in Britain. But there are exceptions, some Norwegian frond dwellers (2) resemble the British.

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.