whereas the foot projects from the wideend. Many species have thin tentacles with adhesive tips. They are used to cap-tureforams,young bivalves, and othersmall organisms from the sediment. Tusk shells are most common in deep water,but empty shells sometimes wash ashore. The monoplacophorans(class Monoplacophora ) are represented by only a handful of limpet-like molluscs. They were thought to be extinct untiltheir discovery as “living fossils” in 1952. They have now been collected, mostly from deep water, in scattered locationsaround the world. Monoplacophoransare peculiar because their gills and otherorgans are repeated along the body, which is reminiscent of the segmentationof annelids