Phragmocone
（重定向自Phragmacone）
![Cutaway of a nautilus shell showing the chambers](/Images/godic/202502/02/NautilusCutawayLogarithmicSpiral5644.jpg")
The phragmocone is the chambered portion of the shell of a cephalopod. It is divided by septa into camerae.
In most nautiloids and ammonoids, the phragmocone is a long, straight, curved, or coiled structure, in which the camarae are linked by a siphuncle which determines buoyancy by means of gas exchange.