Medium sized, 26.5 to 39mm long, 17.5 to 22mm wide. Plates vary from dark green to bright red, with streaks up the sides and they commonly have a dark wedge near the crest. The skirt/girdle protected by overlapping elliptical scales uniform colour but the odd pale area. The front plate densely covered with 13 to 19 smooth to slightly beaded radial ridges, often interspersed with short ridges that don’t go all the way.

Shell sculpture of radial ribs on the head and tail valves, and over the lateral areas of the median valves; longitudinal grooves over the central area, but usually obsolete at the jugum, or crest of the shell. The rear plate with maybe 15 to 20 ridges and the other plates 3 to 5 radial ridges and about 14 short front to back grooves.

Found in the low intertidal zone and below low tide under boulders and stones. North Island.