Biology/Natural History: This anemone-like cerianthid lives in a soft, black, slimy tube that may extend a meter or farther into the sediment. The tube extends slightly above the sediment and is made of a secretion of nematocyst-like organelles called ptychocysts. The cerianthid quickly withdraws into the tube when disturbed, and may leave a star-shaped track in the mud around the tube entrance with its tentacles when it withdraws. Predators include the nudibranch Dendronotus iris, which may be drawn into the tube and continue feeding when the cerianthid withdraws. Dendronotus iris attaches its eggs to the tube of the cerianthid, which appears to be its principal prey. Feeding by the nudibranch usually does not kill the cerianthid. The aboral end of the cerianthid is pointed and adapted to digging. Cerianthids differ from anemones in several ways, such as having an aboral anal pore. Cerianthids have unusually rapidly-conducting nervous systems for Anthozoans. Some cerianthids have fluorescent tentacles.