Calyx—in corals the bowl-shaped depression in the upper part of the skeleton; in stalked echinoderms that part of the body which contains most of the soft parts.
Caprinid—a [Cretaceous] [pelecypod] that is typically coiled in the form of a ram’s horn.
Carapace—the hard protective covering that forms the [exoskeleton] of many invertebrates; in arthropods it is usually [chitinous] or calcaro-chitinous.
Carbonization—the process of fossilization whereby organic remains are reduced to carbon or coal.
Cast—the impression taken from a mold.
Cenozoic—the latest era of geologic time, following the [Mesozoic] era and extending to the present.
Cephalon—the head; in trilobites the [anterior] body [segment] forming the head.
Cephalopod—marine invertebrate with well-defined head and eyes and with tentacles around the mouth; member of class Cephalopoda, [phylum] Mollusca; includes squids, octopuses, pearly nautilus.
Ceratite—an ammonoid [cephalopod] with [suture] composed of rounded saddles and jagged lobes; member of subclass Ammonoidea.
Chert—a cryptocrystalline [variety] of [silica]; flint is a variety of [chert].