Cestum veneris has the standard ctenophore body plan pulled out of shape. The oral-aboral axis, which in a typical comb jelly runs from mouth to statocyst, is compressed, while the tentacular axis is drawn out into a ribbon that can pass a metre in length and only a few centimetres wide.
Four of the eight comb rows are reduced and two run along the upper edge of the ribbon, so the diffraction shimmer travels the animal's whole length. Small tentacles line a groove along the lower margin and collect plankton, which is passed to the mouth at the ribbon's centre. Locomotion combines that ciliary beating with muscular undulation, a snake-like ripple that most ctenophores do not use, and the animal can accelerate away when disturbed.
The body is transparent and often faintly iridescent, and the species is bioluminescent, capable of a blue-green glow when disturbed at night. The name records how the animal looked to eighteenth-century naturalists: a belt or girdle. It is worth stressing that despite its appearance it is not a worm, not a jellyfish, and has no stinging cells.