Length 4.1 mm. An open, narrow mantle cavity runs around the whole animal. It contains about six red gills (1) on either side close to the posterior (merobranch arrangement) . Between the foot and hyponotum, the unobtrusive mantle fold (2) helps the foot, when expanded, to seal the mantle cavity into a closed tube containing the gills.
Dorset, England. February 2018. Leg. S. Trewhella.