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The glossary provided here is largely based on “Seashells of Southern Florida: Bivalves,” by Paula M. Mikkelsen & Rüdiger Bieler, Princeton University Press. Production of this glossary was funded in part by the National Science Foundation’s Partnerships in Enhancing Expertise in Taxonomy [PEET] Program, NSF-DEB-9978119, “Bivalves - Research, Training, Electronic Dissemination of Data” (1999-2008) to Bieler and Mikkelsen.
- CAECUM (pl. CAECA)
A blind pouch on an anatomical structure, such as the STOMACH or MANTLE; see also TUBULE (figure: Teredinidae).
- CALCITE (adj. CALCITIC)
- A form of calcium carbonate found in molluscan shells and other hard parts; see also ARAGONITE, which differs from calcite in certain characters of crystallization and density.
Accessory shell or periostracal plate closing the anterior gape in adults of Pholadidae (figure: Martesia striata).
- See PERICALYMMA.
External shell sculpture consisting of COMMARGINAL and radial elements crossing to form a grid- or net-like pattern; also called reticulate (figure: Semele bellastriata).
- CARDINAL AREA
Flattened area between the UMBONES dorsal to the HINGE TEETH; also called FOSSETTE (figure: Noetia ponderosa).
- CARDINAL TEETH
HINGE TEETH originating below the UMBO (figure: Polymesoda floridana).
- Enzyme that facilitates the reduction of plant material by catalyzing the hydrolysis of cellulose.
- CEPHALIC EYE
- See EYE.
- CEPHALIC HOOD
A covering over the external ADDUCTOR MUSCLES inserted on the UMBONAL REFLECTION in Pholadidae (where it is composed of periostracum, found only in juveniles, and replaced by one or more ACCESSORY PLATES in adults) and in Teredinidae (where it is formed by an extension of the MANTLE) (figure: Teredinidae).
- CHALKY DEPOSITS
- Irregular, porous, white deposits of unknown cause or function on the interior shell surface (in Ostreidae).
An elongated tube of solid material, here either (1) composed of feces and/or pseudofecal particles cemented with mucus, fitting over the posterior end of the shell, sometimes far anteriorly, in members of Pholadidae, or (2) an extension of the calcareous burrow lining in Gastrochaenidae (see figure), that projects above the surface of the substratum (figure: Gastrochaenidae).
Elongated, sinuous, and/or pustular interlocking ridges on the COMMISSURAL SHELF on each side of the LIGAMENT, ranging from simple tubercles-and-sockets to a complex anastomosing network (see Ostreidae, Gryphaeidae); those of Gryphaeidae are elongate and worm-like and are called VERMICULAR CHOMATA (figure: Hyotissa mcgintyi).
A type of RESILIFER, commonly spoon-shaped and (in some species) buttressed and projecting below the HINGE for insertion of the RESILIUM, especially characteristic of Mactridae and Myidae (figure: Anatina anatima).
- CILIATED DISKS
Ciliated pads that conjoin in "velcro" fashion to connect two soft-tissue surfaces, for example in PROTOBRANCH or ELEUTHERORHABDIC CTENIDIA.
- CLASPER SPINES
Shelly outgrowths of the external valve surface that wrap around and secure the bivalve to a narrow solid substratum (see Ostreidae: Lophinae) (figure: Dendostrea frons).
- See CLASPER SPINES.
Sculpture parallel to the shell margin, also called concentric (figure: Astarte crenata subequilatera).
- COMMISSURAL SHELF
A demarcated shell margin defined interiorly by an angle with the main body of the shell (see Ostreidae, Gryphaeidae) (figure: Hyotissa hyotis).
- COMPENSATION SACK
- See SEPTAL VALVULA.
- COMPLEX CROSSED LAMELLAR
- See CROSSED LAMELLAR.
- See COMMARGINAL.
Knob-like internal structure (usually one dorsal, one ventral on each valve) at the valve margins in Pholadidae and Teredinidae, which in pairs form pivoting points upon which the valves articulate during the boring process (figure: Martesia striata).
- CROSSED LAMELLAR
- Shell microstructural variety consisting of adjacent aggregations of numerous, parallel, elongated, aragonitic elements arranged in two predominant directions relative to the shell margin; the units in COMPLEX CROSSED LAMELLAR microstructure are arranged in three or more directions.
- CRUCIFORM MUSCLE
Cross-shaped muscle at the base of the INCURRENT SIPHON in Tellinoidea (and recognized as a SYNAPOMORPHY of that superfamily) that absorbs the physical strain experienced when the SIPHONS extend and retract; associated with paired sensory organs thought to monitor water quality.
- CRURA (pl. CRURAE)
- Incorrect Latinization of crus (pl. crura), but frequently found in the malacological (and medical) literature in this form; see CRUS.
- CRUS (pl. CRURA)
Variously used term (often incorrectly Latinized as crura, crurum, or crurae) for (1) a raised ridge resembling a tooth (in, e.g., Pandoridae), (2) an opposed internal shell rib in Pectinoidea (see figure), or (3) the specialized stalked RESILIFER of Anomiidae (figure: Caribachlamys sentis).
- See IGLOO.
- CRYSTALLINE STYLE
Rod-shaped inclusion in the STOMACH of many mollusks, including most bivalves, that includes the starch-digesting enzyme AMYLASE (possibly also CELLULASE for reduction of phytoplankton) and that reduces the size of ingested food particles through rotating abrasion against the gastric shield (and chitinous lining if present); produced by secretory tissues in the STYLE SACK; believed homologous with the PROTOSTYLE of Protobranchia, which does not include AMYLASE; see also STOMACH, PROTOSTYLE.
- CTENIDIAL EYE
- See EYE.
- CTENIDIUM (pl. CTENIDIA)
Gills, or organ of respiration and in most cases also of food-gathering in bivalves; usually suspended by tissue or cilial junctions from the dorsal region of the animal and typically comprising a W-shaped doubly folded lamella on each side of the visceral mass; each side typically consisting of an inner and outer DEMIBRANCH (HOLOBRANCH = entire gill), each of these with an ascending and descending lamella and often with ciliated food grooves at the distal edges and/or at the junction of the two demibranchs, also with or without interlamellar junctions connecting the two lamella of one demibranch; see also EULAMELLIBRANCH, FILIBRANCH, HETERORHABDIC, HOMORHABDIC, PROTOBRANCH, PSEUDOLAMELLIBRANCH, PLICATE, SEPTIBRANCH, SYNAPTORHABDIC (figure: Mercenaria mercenaria).
Comb-like row of denticles along the ventral edge of the BYSSAL NOTCH in Pectinidae; also called pectinidium or pectineum (figure: Caribachlamys sentis).
- Multiple segments of an IGLOO cemented superficially to hard substratum by Cucurbitula (Gastrochaenidae), creating an artichoke- or pine-cone-like external appearance.
- HINGE type characterized by a small or absent hinge plate, and teeth that essentially emerge from hinge margin, for example, in Cardiidae.