The anterior quarter of the sole is axehead shaped, and the posterior three quarters are spearhead shaped. It is translucent white with opaque white spots, and the internal opaque white, ‘V’ shaped, anterior pedal mucous gland (1) may be indistinctly visible. The opening of the posterior pedal mucous gland (2) is just behind the centre point. This gland secretes adhesive mucus that is shaped by a medial groove on the posterior half of the sole into strong threads that harden on contact with sea water and are used to help secure the snail in its movement around plants. Shell height 7.4mm. Orkney, Scotland. May 2017. Leg. S. Taylor & 9.25mm. Orkney. April 2018.Leg. I.Williamson.
21 Rissoa membranacea.
