Chitin—a horn-like substance, found in the hard parts of many animals, such as beetles, crabs, etc.
Chitinous—composed of [chitin].
Cirri—in crinoids, the jointed appendages which branch off the side of the stem or from the base of some crinoid stems.
Coelenterate—invertebrates characterized by a hollow body cavity, radial [symmetry], and stinging cells; a member of [phylum] Coelenterata; includes jellyfishes, corals, sea anemones.
Colonial—in biology refers to the way in which some invertebrates live in close association with, and are more or less interdependent upon, each other; [colonial] corals, hydroids, etc.
Columella—a small column or central axis; in corals the small rod or axial pillar in the center of the [corallite]; in gastropods the solid or perforate pillar formed by the union of the successive coils of a conispiral shell.
Columnal—one of the disk-shaped segments of a crinoid stalk.
Concentric—having a common center, as circles; refers to shell markings that are parallel to shell margin.
Concretion—nodular or irregular masses in sedimentary rocks and usually formed around a central core, which is often a [fossil].
Conical—cone-shaped.