22 Rissoa membranacea

22 Rissoa membranacea

The opercular disc extends beyond the operculum as prominent, translucent, whitish, opercular lobes (1) that are unpigmented except proximally (2) where the thick disc merges with the dark exterior of the columellar muscle. Within the mantle cavity there is a large penis on males (3).  Shell height 7.4 mm. Orkney, Scotland. May 2017. Leg. S. Taylor.

marinvert.senckenberg.science/image-browse/