"Aptychus" is a word in ENGLISH

One of a pair of shelly plates found in some cephalopods, as the ammonites.

A division of Amphineura in which the body is naked or covered with slender spines or setae, but is without …

The shelly skeleton of a sea urchin.

A stomach armed with chitinous or shelly plates or teeth, as in certain insects and mollusks.

Of or pertaining to an oyster, or to a shell; shelly.

One of a pair of shelly plates that protect the siphon tubes of certain bivalves, as the Teredo. See Illust. …

A shelly concretion, usually rounded, and having a brilliant luster, with varying tints, found in the mantle, or between the …

A division of gastropod Mollusca, including the chitons. The back is covered by eight shelly plates. Called also Polyplacophora. See …

punga n operculum, a shelly plate attached to the foot of gastropod mollusks which covers the mouth part of the …

Abounding with shells; consisting of shells, or of a shell.

Any bivalve mollusk which secretes a shelly tube around its siphon, as the watering-shell.

Shelly.