1: brown longitudinal band on dorsal surface of snout, head and neck.
2: ground colour of flesh translucent white with opaque white spots.
3: no eye at base of tentacle (usual position on Caenogastropoda, R. diaphana is in the Heterobranchia).
4: eye situated far back from tentacles; rare protrusion of it beyond aperture rim.
5: brown diagonal band on side of the foot.
6: copious mucus exuded by mantle.
7: brown opercular lobes.
Shell height 1.6 mm, Anglesey, Wales, May 2016.