The Phoronida, also known as horseshoe worms, is a phylum of marine, tube-dwelling, worm-like animals generally less than 800 millimeters (8 inches) long. In phoronids the gut loops and ends close to the mouth, instead of passing straight through the body as in annelids and many other wormlike organisms. The mouth is surrounded by the ciliated feeding structure known as a lophophore. Each individual lives with its tube buried in sand or attached to a rock or shell in shallow temperate or tropical seas. Most species are colonial.