Length 4.1 mm. The expanded foot is an elongate ellipse, broader at the front than at the posterior. When live and in good condition, the sole is a striking carmine red but less intensely, as here, when expanded.
Between the foot and hyponotum, the unobtrusive mantle fold (1) helps the foot, when expanded, to seal the mantle cavity into a closed tube containing the gills.
Dorset, England. February 2018. Leg. S. Trewhella.