(Definitions after Holmes, 1979; Smith, 1996)

adductor muscle (Mollusca: Bivalvia) - the muscle which closes the valves.

alivincular (Mollusca: Bivalvia) - ligament not elongated, positioned between cardinal areas of valves (areas around hinge).

amphidetic (Mollusca: Bivalvia) - extending behind and in front of umbo.

aperture - the opening of a gastropod shell.

apex - the tip of the spire of a shell.

bivalve - a shell consisting of two hinged valves.

body whorl - the large final coil of a gastropod shell that contains the body.

calcareous (of operculum) - an operculum consisting of calcium carbonate.

carinate - with a keel.

decollate (Mollusca: Gastropoda) - with shell apex broken off.

dentate (Mollusca: Bivalvia) - with teeth.

dextral (Mollusca: Gastropoda) - with aperture on observers right if shell is held with aperture towards observer and spire uppermost (see sinistral ).

digitate - finger-like.

edentate (Mollusca: Bivalvia) - without teeth.

elongate - long.

equilateral (Mollusca: Bivalvia) - the same on each side (of an axis).

equivalved (Mollusca: Bivalvia) - both valves similar in shape and size (Purchon, 1977).

filiform (Mollusca: Gastropoda) - with frond-like tentacles.

fusiform (Mollusca: Gastropoda) - spindle shaped shell, tapering at both ends.

gastropod - single-shelled mollusc.

globose - spherical or globular in shape.

glochidian larva - the parasitic larva of some freshwater bivalves.

helicoid ( helical ) - spirally coiled.

hinge - the place of junction of two bivalve shells.

horny (of operculum) - comprising horn-like conchin.

inequilateral (Mollusca: Bivalvia) - in the horizontal plane of a single valve: Drop a perpendicular line from the umbo . . . [the shell] divides into a smaller anterior part and a larger posterior part (Purchon, 1977).

inequivalved (Mollusca: Bivalvia) - valves dissimilar in shape and size (Purchon, 1977).

keel - longitudinal ridge.

lamellar hinge - hinge of bivalve made by long, thin teeth lying side by side.

ligament (Mollusca: Bivalvia) - elastic material hinging a bivalve and functioning in its opening (Smith and Kershaw, 1979).

limpet - mollusc with a non-coiled, roof-like, moderately elevated shell.

mantle - fleshy/membraneous covering of the anterior parts of the body of a gastropod, or the entire body of a bivalve mollusc.

marginal gape (Mollusca: Bivalvia) - gap between valves when fully closed.

marsupium (Mollusca: Bivalvia) - pouch in gills in which young are reared in ovoviviparous species.

nacreous/nacre (Mollusca: Bivalvia) - interior with a pearly ('mother-of-pearl') appearance.

neritiform - shaped like a member of the Neritidae - with a very round shell and sunken spire.

nodule - a raised bump on the shell.

operculum - a horny or calcareous plate that closes the aperture when the animal retreats into a shell.

opisthodetic (Mollusca: Bivalvia) - posterior to umbo.

pallial line (Mollusca: Bivalvia) - line left by mantle on shell.

parietal lip - the inner wall of the shell aperture of a gastropod.

parivincular (Mollusca: Bivalvia) - ligament elongate and cylindrical, posterior to shell beaks (Allaby, 1992).

patelliform (Mollusca: Gastropoda) - limpet-like ('pan shaped').

peristome (Mollusca: Gastropoda) - region surrounding the shell aperture.

planispiral (Mollusca: Gastropoda) - shell coiled in a flat spiral.

pneumostome (Mollusca: Gastropoda) - breathing hole into pulmonary cavity of pulmonates.

pyriform (Mollusca: Gastropoda) - pear-shaped.

radula - the ribbon-shaped structure bearing rows of teeth used in feeding.

reticulate - a network pattern.

sculpture (Mollusca: Bivalvia and Gastropoda) - surface ornament of the shell.

sinistral (Mollusca: Gastropoda) - with the aperture on the observers left if shell held with aperture towards observer and spire uppermost (see dextral (Williams, 1980)).

spire - all the coils of a shell above the body whorl.

subglobose - depressed globose shape.

suture - the junction between whorls of a gastropod shell.

tentacles - the sensory projections from the head of a gastropod.

umbilicus (Mollusca: Gastropoda) - chink between reflected inner lip of shell aperture and the first body whorl (of shell).

umbo (Mollusca: Bivalvia) - a beak, protuberance on each valve above the hinge, larval shell.

whorl - one complete spiral turn of the shell of a gastropod.