|Image: National Museums Northern Ireland|
Nereiphylla paretti is a 30 cm (foot) long worm from European waters like the North Sea, English Channel and Mediterranean. They're active predators who scour the shallows in search of prey.
Nereiphylla paretti is an annelid, or segmented worm, so-called because its body is divided into segments.
More precisely it's a polychaete, also known as a bristle worm, because each segment bears a collection of tough bristles sprouting out of the sides.
Even more precisely it's a Phyllodocid, or paddle worm, because some of those bristles have turned into large, flattened paddles.
I don't know what these paddles are for but man, when each one is edged with yellow it sure looks pretty!