Trophic classification. Appreciation of the ecologic functions of echinoderms is derived from an understanding of the diverse feeding methods and food preferences found within the group. Echinoderms are dominantly benthonic marine organisms but exploit a wide variety of food resources on the bottom, within the sediment, and from the water masses near the bottom (Table 1). The only echinoderms that are not strictly benthonic are some of the elasipodid holothurians, which have been captured at the surface and swimming above the bottom at great depth (Barnes et al., 1976). By rhythmic undulations of a fan of oral tentacles these bizarre holothurians capture suspended food particles from the water mass near the sea floor. Their anomalous form and habits, so far removed from the typical sea cucumber, serve to emphasize that holothurians and all other echinoderms cannot be readily characterized by a single trophic classification for each group. Each major living group of echinoderms has diversified in feeding methods and/or food preferences.