Either of two genera of
The pearly, or chambered, nautilus (genus Nautilus ) lives in the outermost chamber of its smooth, coiled, usually 36-chambered shell, about 10 in. (25 cm) in diameter. A connecting tube adjusts the gases in the chambers, allowing the shell to act as a float. Nautiluses search the ocean bottom for shrimp or other prey, which they capture with up to 94 small, suckerless, contractile tentacles. The paper nautilus (genus Argonauta ) feeds on plankton near the surface of tropical and subtropical seas. The female resembles an {{link=octopus">octopus but has a thin, unchambered, coiled shell, 12–16 in. (30–40 cm) in diameter. The much smaller male has no shell.
Chambered nautilus ( Nautilus )
Douglas Faulkner