Lancelet (Branchiostoma lanceolatum)).
Cephalochordata is a subphylum of the phylum Chordata (see chordates) containing marine fish-like animals that differ from fish by lacking bone or cartilage, paired fins, jaws, and teeth. In Cephalochordata the notochord persists into adulthood. The best known member is the lancelet (amphioxus) which is capable of short bursts of swimming activity, but spends most of its life partially buried in sand. It feeds on particles filtered from the water.