Uneroded valves i to vii have a distinct posterior beak (1) and, on each side, a triangular, lateral area (1 – 2 – 2) and a triangular pleural area (1- 3 – 3). Sensory aesthetes open on the dorsal surface as small pores in a pattern of quincunxes. Small black spots in the aesthetes of the lateral areas are light sensitive, intrapigmental aesthetes. Orkney, Scotland, February 2015. Leg. P. Lightfoot.