Spirorbis corallinae is a very small (1-2 mm) coiled polychaete (bristle worm) that lives attached to seaweed in shallow saltwater.

It has a smooth, white or semi-translucent, sinistral (left-handed) coiled shell encasing an orange body about 1.5 mm in length.

The worm has a short abdominal region and a slightly broader thorax terminating in colourless tentacles, used to filter food from the water.

The Spirorbis genus are cross fertilising hermaphrodites, who brood their 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.