A fossil shell of an oyster-like mollusc.

The stony inner cast of the fossil Trigonia.

Palaeontology. The phragmocone of a belemnite. Obsolete.

A fossil orthoconic shell of a nautiloid cephalopod mollusc of the Palaeozoic or early Mesozoic eras; spec. a member of the genus Orthoceras…

A fossil shell of a nautiloid cephalod mollusc of the Palaeozoic or early Mesozoic eras, having a long, straight (or nearly straight) chambered…

Palaeontology. In early use: the fossilized phragmocone of a belemnite. In later use: the conical chamber which, in many belemnites, lies at the…

A fossil volute.

A fossil stromb or some similar shell.

A fossil snail-shell.

A fossil turbinate shell.

The chambered part of the shell in some cephalopods; esp. the conical chambered internal shell of a belemnite.

An anterior prolongation of the guard or rostrum of a belemnite or other fossil cephalopod, usually long and flat.

= orthoceratite, n.

A long, slender, tubular extension of the sicula in a graptolite.