Small flat chiton, 15-25mm in length, usually oval with some individuals almost round. Crests of the valves are smooth with radial ribs and granular grooves running down to the edges, the whole usually light greenish with darker blotches. The yellowish brown girdle is relatively wide and is covered in spicules. There are tufts of white bristles along the inner girdle at the base of each valvesuture and at the head, with shorter bristles surrounding the margin poking outwards. P. egregia hollows out a cavity in bull kelpholdfasts, usually on exposed rocky coasts, from low intertidal to shallow subtidal zones. Found from Cook Straitsouth to Stewart Island.