Mantle extends near centre of shell from apical slit as pale yellow exhalent siphon (3) and rounded, densely lobular, anterior (4) and posterior (2) lappets (brown on adults). Surviving protoconch(1) to posterior of siphon concealed by growths and debris. Mantle skirt pale yellow (5).
Juvenile, length 5.5 mm. Menai Strait, Wales. March 2015.