15-54 mm. —> Thick, subcircular, or slightly fan-shaped shells with eight to twelve strong irregular ribs or folds (plications). Lower valve attaches near the umbo to the substrate. UV with large or small smooth umbonal disk, not to be confused with the attachment area of the lower valve. Cream color with short fine radial lines of orange to red. (40 mm) Distribution: Abundant in the Gulf of Suez. Rare elsewhere.
Notes: Some specimens have many more than the expected number of ribs, even up to 34. These usually, but not always, have a very large attachment area. This may be an undescribed species or a very rugged form of P. australis. Or P. plicata may exhibit more variation than previously recognized. Other specimens have steep angular ribs.