[1] S. spirorbis is a cross-fertilising hermaphrodite that broods its young in a tube attached to the worm inside the shell.

The larvae are released at an advanced stage of development and spend just a few hours as free-living organisms before attaching themselves to the nearest suitable surface, often the same seaweed as the parent.

[2] The species has a smooth, white, sinistral (left-handed) coiled shell encasing an orange body about 3 mm in length.

[citation needed] The worm has a short abdominal region and a slightly broader thorax terminating in ten stiff tentacles, used to filter food from the water.

In a study, where fronds of Fucus serratus already colonised by adults were available for settling, the larvae avoided the most densely populated areas and favoured the concave grooves on either side of the midribs.