Nautilus

Nautilus, or chambered nautilus, genus of shellfish native to the South Pacific and Indian oceans, having a spiral shell divided into chambers. As the nautilus grows it adds on new and larger chambers, sealing off the old ones and living in the new ones. The nautilus breathes by means of gills and uses tentacles to catch the animals on which it feeds. It is a member of the class of cephalopods (which includes squid and octopi), mollusks with a tubular siphon and a circle of tentacles around the head.