chaetognath

any small wormlike marine invertebrate of the phylum Chaetognatha, including the arrowworms, having a coelom and a ring of bristles around the mouth

Any of various small, wormlike marine invertebrates of the phylum Chaetognatha, having often transparent or translucent bodies that are pointed at one end. The head has small hooks for grasping prey, and it contains a large cerebral ganglion of sensory nerves. Chaetognaths are popularly called arrowworms, and are thought to be related to the echinoderms and chordates.