The Subphylum Cephalochordata contains about 30 species of small animals called lancelets.  Although they can swim fairly well, most animals are found with their tails buried in the sand with only the anterior end protruding.  Like the tunicates, lancelets are filter feeders.  They take in food and water through an oral hood whose edges bear delicate projections called cirri that act as a strainer to exclude larger objects.  Inside of the oral hood are bands of cilia that sweep food into the mouth. Cilia on the pharyngeal gill slits drive a current of water through the pharynx, which then enters a chamber called an atrium to exit out an opening called the atriopore. Although a small and relatively obscure group by some standards, current evidence suggests that the cephalochordates were most likely the direct ancestors of the vertebrates, which certainly makes them worthwhile subjects for study!