ChambersThe closed rooms of the coiled shell. A grown nautilus has about thirty of them.
SeptaThe curved walls between the chambers. The animal builds a new one each time it moves forward.
SiphuncleA thin tube of living tissue through every chamber. It runs from the body back to the middle of the spiral.
Body chamberThe last and largest chamber, open to the outside. The animal lives in this one only.
Opening (aperture)The open end of the body chamber. The animal can pull in and close it with its hood.
The animal 6
HoodA tough, leathery flap above the head. It closes the opening when the animal pulls into its shell.
TentaclesMany slender arms with no suckers. Each one slides back into a sheath of its own.
EyeA simple eye with no lens. Light enters through a small pinhole, as in a pinhole camera.
FunnelA short tube under the tentacles. Water squirted out through it pushes the animal along.
MantleThe fold of skin that makes the shell. Its free edge forms a flap around the head.
ShellA flat spiral coiled in one plane. Its upper side is marked with irregular stripes.
How this list was compiled: Every name was checked on 2026-10-03 in at least two sources, for facts only and with nothing copied. T. J. Parker and W. A. Haswell, A Text-book of Zoology, volume 1 (1910, public domain), the pearly nautilus, https://archive.org/details/textbookofzoolog00park. Wikipedia: Nautilus, Chambered nautilus, Siphuncle and Aperture (mollusc), https://en.wikipedia.org/wiki/Nautilus. Animal Diversity Web, University of Michigan Museum of Zoology, Nautilus pompilius, https://animaldiversity.org/accounts/Nautilus_pompilius/. A university aquarium's marine life profile of the chambered nautilus, https://web.archive.org/web/20060924223738/http://www.waquarium.org/MLP/root/pdf/MarineLife/Invertebrates/Molluscs/Nautilus.pdf. R. W. Hegner, College Zoology (1912, public domain), the chambered nautilus, https://archive.org/details/collegezoology00hegn. Unofficial study material, not affiliated with any textbook, course or exam; check your own course material. Licence: own work
The drawing: Drawn for this site on 2026-10-03 from plain geometry; nothing traced. Licence: own work
How it works
This nautilus shell is labeled in two views. The first shows a chambered nautilus shell cut in half, with its chambers, septa and siphuncle. The second shows the living animal looking out of its shell.
Read the full guide
The shell cut in half
The shell is a flat spiral divided into chambers by curved walls called septa. A thin tube, the siphuncle, runs through every chamber. The animal lives only in the last and largest room, the body chamber, which ends at the opening.
The animal
The second view shows the nautilus in its shell. The hood sits above the head, with the eye just below it. The tentacles spread out in front and the funnel lies under them. Press Quiz me to find each part.
The oldest chamber is the smallest one, at the center of the spiral. Each newer chamber is larger than the one before.
Questions and answers
How many chambers does a nautilus shell have?
About four when the animal hatches and about thirty when it is fully grown. As it grows it moves forward in its shell and seals off the space behind it with a new wall.
What is the siphuncle of a nautilus?
A thin tube of living tissue that runs from the body through every chamber of the shell. It helps the animal control how well it floats.
What are the walls inside a nautilus shell called?
Septa. Each septum is a curved wall that closes off one chamber from the next. The siphuncle passes through the middle of every one.
Does a nautilus live in its whole shell?
No. It lives only in the last and largest chamber, called the body chamber or living chamber. The older chambers behind it are sealed and hold gas, which keeps the animal from sinking.
How does a nautilus see?
With two simple eyes that have no lens. Each works like a pinhole camera, so the picture it gives is a simple one. The nautilus finds much of its food by smell.