Mollusks all have four things in common: a visceral mass, a mantle, a foot, and a radula. The visceral mass is the region that contains the body organs; the mantle is the top body wall that covers the visceral mass and usually sticks out as flaps; the foot is the underside of a mollusk and it is differentiated for each individual species, for example snails have a different underside than octopuses; radula are minutely toothed, chitinous ribbon, which is usually used for scraping or cutting food before it goes down the esophagus.