Shell small, average length 20 mm. (0,75 of an inch) but grows up to 30 mm. (1,125 inches), irregularly to regularly star-shaped, with eight prominent radial ribs that project to a varying extent; irregularly and weakly lobate in typ¬ical chapmani, regularly and strongly projecting and narrowly-pointed in the form perplexa. Surface sculptured with numerous radial, weakly-scabrous lirae, the centre one down each of the eight radial folds being stronger than the rest. Colour of exterior buff, with scattered flecks of light-brown, and often, especially in the perplexa form, with a narrow reddish brown line down the crest of each of the eight radial folds. Interior porcellanous-white, without a clearly defined spatula. Radula: Formula 3 + 1 + (2+1+2) + 1+3. Central teeth five, the middle one only half the size of the other four, lateral massive with four cusps, and the three marginals long and slender, each with a weak blunt cusp.
Length: 18-30 mm; Width: 16-28 mm; Height 4-12 mm.

Shell ovate, somewhat broad behind; reddish or scorched and nebulously brown; apex acute, submedian; with eight radiating ribs more or less valid, and depressedly rounded, profusely radiate with very fine lirae, and girdled with irregular sulci; margin angulate, nodulose; white within and clouded pale rose; spatula scarcely visible. Size: 0,75 inch.
This shell shows considerable variation in form, due to environment. Those on surf-beaten rocks are flat and eight ribbed, while those living in more sheltered situations are taller with the eight ribs far less prominent. The variations have been given a number of names including Patella perplexa Pilsbry, 1891, and Patella alba Tenison Woods, 1876.

This is a small white limpet that assumes different outlines, varying from irregularly-lobed to a regular 8-pointed star. This latter form, more common in New South Wales is the "Acmaea saccharina var. perplexa" of Pilsbry, 1891. It lives in the lower littoral zone among algae on rock platforms and boulders.

Southern half of Australia and Tasmania.