Glossary

Words in pop-up glossary. A technical glossary of shell features is also available.

abapical

away from the apex of the shell.

adapical

towards the apex of the shell.

apical

at the apex.

benthic

(adj.) living on the bed of the sea, river, lake etc.

bifid

divided into two parts by a cleft.

bipinnate

(of gill plume) twofold branching; boughs and branches, but no subsequent twigs; in one plane like a feather.

caruncle

fleshy excrescence like neck wattle on turkey.

cephalic shield

shovel-like layer covering front part of philinid sea slugs.

ceras

(singular) lobe on sides or back of aeolids and some other sea slugs.

cerata

(plural) lobes on sides and back of aeolids and some other sea slugs.

chitin

semitransparent flexible horny material.

chitinous

(adj.) made of chitin.

chromatophores

tiny elastic pigment spots which can cause rapid change to body colour by expansion /contraction.

cilia

mobile linear extensions of membrane used in feeding or locomotion.

cnidaria

hydroids, jellyfish, sea anemones etc.

cnidosac

storage capsules for unexploded cnidaria stings at tips of cerata.

conchiolin

horny material used to make outer layer of operculum.

concolorous

the same colour as.

costa

strong rib running across a whorl of a gastropod shell.

costae

strong ribs running across a whorl of a gastropod shell.

ctenidia

(pl.) comb-like molluscan gills; usually an axis with a row of filaments either side.

ctenidium

comb-like molluscan gill; usually an axis with a row of filaments either side.

digitiform

shaped like a finger.

distal

away from centre of body or point of attachment.

dorid

a sea slug in the infraorder Doridacea; with gills and rhinophores on the dorsum; often shaped like half a lemon or grape.

echinospira

special form of drifting larva with an inner and outer shell, the intervening space filled with sea water.

EHWS

extreme high water spring tide (usually near March and September equinoxes).

ELWS

extreme low water spring tide (usually near March and September equinoxes).

endo-skeleton

skeleton supporting body from within.

epipodial

(adj.) of the epipodium (collar or circlet running round sides of foot of some gastropods)

epipodium

<p>collar or circlet running round sides of foot of some gastropods, bearing bosses, lobes and / or tentacles</p>

epithelium

tissue forming outer layer of body surface.

epizooic

of non-parasitic sedentary animals living attached to other animals.

euryhaline

able to tolerate a wide variation in salinty.

fusiform

slender, spindle-shaped, tapering almost equally towards both ends.

gladius

quill-like pen of chitin serving as muscle attachment and support in squid etc.

hectocotylus

specialised arm on male octopus, squid etc adapted for transfer of spermatophores into female’s mantle cavity

height

1. of gastropod shells: distance from apex of spire to base of aperture. 2. of bivalve shells: distance from hinged dorsal edge to opening ventral edge.

holobranch

(of chitons) gills in groove along side of foot extend full length of foot.

kamptozoa

same as entoprocta, tiny filter feeding goblet shaped animals.

labial varix

very strong or broad costa along outer edge of aperture.

lamellae

(of sea slugs) small plates on rhinophores. (of bivalves) folded layers of ctenidium.

laminae

(sing. lamina) thin flat plates

LWS

<p>low water spring tide, two periods of a few days each month when tide falls lowest.</p>

mantle

sheet of tissue that secretes the shell and forms a cavity for the gill in most marine molluscs (but not in adult nudibranchs), part or all of dorsal body surface when shell absent or internal.

merobranch

(of chitons) gills, in groove along side of foot, only in posterior half of animal.

mesial

on or directed towards the midline of the body.

metapodium

hind part of the foot.

MHW

mean high water level.

MHWS

mean high water spring tide level (level reached by highest tides for a few days every fortnight, Pelvetia zone on rocky coasts).

MTL

mid tide level.

nekton

(collective noun) animals that swim freely in pelagic zone (main body of water). cf. "plankton".

nektonic

(adj.) swims freely in pelagic zone (main body of water).

nematocysts

ejectile toxic stings produced by hydroids, sea anemones etc. (Untriggered ones are ingested by predating aeolid sea slugs and stored at the tips of their cerata for defence.)

neuston

community of micro-organisms living in the surface film of water

notal

(adj.) of the back.

notum

(of sea slugs) the dorsal surface.

operculum

horny plate, sometimes calcareous, used to close shell aperture.

oral tentacles

pair of tentacles on or near anterior edge of head near mouth.

oral veil

flat anterior extension of head.

osculum

large exhalent opening on some sponges.

oviparous

(adj.) embryos develop in egg after laying.

ovotestis

hermaphrodite organ serving as both ovary and testis

ovoviviparous

(adj.) embryos develop inside egg within mother (but separated from her by persistant egg membrane). Young born from mother after, or as, eggs hatch.

p.p.t.

<p>(salinity) parts salt per thousand parts water (brackish &lt;30ppt).</p>

pallial

(adj.) of the mantle.

pallial line

(on bivalves) internal line parallel to ventral margin of valve, marking attachment position of mantle lobe.

pallial sinus

(on bivalves with long siphons) indentation in pallial line near posterior of valve where siphons withdraw.

parapodial lobes

flaps of the parapodium (fleshy structure used in locomotion) which extend up the sides of some opisthobranch molluscs.

parthenogenetic

(adj.) reproducing without fertilization by male.

pen

quill-shaped chitin serving as muscle attachment and support in squid etc.

pericardium

sac containing heart, visible behind rhinophores in translucent aeolid sea slugs.

periostracum

thin horny layer of chitinous material often coating shells.

plankton

<p>animals and plants that drift in pelagic zone (main body of water). cf. 'nekton'.</p>

propodial

at the front of the foot.

prosocline

adapical end of growth line or costa tilted forward of the abapical end, so is nearer the aperture.

proximal

towards the centre of the body or point of attachment.

rhinophores

chemo-receptor tentacles; nudibranch sea slugs have a pair on top of head.

rugose

roughened, corrugated or wrinkled.

sepia

ink ejected by cephalopods (octopus, squid, cuttlefish).

sessile

1. of immobile animals living attached to substrate, other animals, seaweed etc. 2. lacking a stalk.

siphon

extension of mantle to form a channel for respiratory water current.

siphonal canal

grooved or tubular extension of outer lip of the shell aperture on some snails, to support the siphon.

stenohaline

unable to tolerate a wide variation in salinity.

subapical

just below the apex.

subepidermal

below surface of skin.

sublittoral

below level of low water spring tide

subterminal

a short distance from the end.

suture

groove or line where whorls adjoin.

tripinnate

(of gill plume) threefold branching; "boughs, branches, twigs" in one plane like a feather.

umbilical chink

narrow slit opening of umbilicus on some gastropods

umbilicus

cavity up axis of some gastropods, open as a hole or chink on base of shell, often sealed over.

unipinnate

(of gill plume) branching singly; boughs but no subsequent branches or twigs, in one plane like a feather.

varix

(pl. varices). Very strong or broad costa (rib) along edge of aperture (labial varix), or at previous position of labial varix during growth.

varnish

layer of material applied to (usually) inside of conchiolin layer of operculum.

veliger

shelled larva of marine gastropod or bivalve mollusc which swims by beating cilia of a velum (bilobed flap).

velum

bilobed flap on veliger larva, with beating cilia for swimming.