Pictorial Key | ID Keys | Marine Bivalve Shells of the British Isles

Not sure


Shoreline - 500m deep (including shells found on beaches)	500m - 4000m+ deep

Not sure

Shell outline ratio
Not sure


Longer than High	Equal	Higher than Long

Valve Symmetry: equivalve or inequivalve
Not sure


Equivalve (valves the same dimensions)	Inequivalve (valves differing in size or shape)

Valve Lateral form: equilateral or inequilateral
Not sure


Equilateral (posterior and anterior areas equal)	Inequilateral (posterior and anterior areas not equal)

Visibility of the Ligament
Not sure

Visible externally

Not visible externally

Primary Sculpture
Not sure


Predominantly Radial	Predominantly Concentric	Equally Radial and Concentric

Smooth / no sculpture	Other Sculpture

Secondary Sculpture
Not sure


No secondary sculpture	Microsculpture

Coloured rays	Bristles

Lamellae, spines or projections

Not sure


Taxodont (simple projections in a row along the dorsal margins)	Dysodont (No true teeth, only small, ill-defined denticles)

Heterodont (teeth are few in number in two distinct forms, *Cardinal* and *Lateral*)	Isodont ( The teeth are ridge like or rectangular and are called crura, and placed symmetrically either side of the ligament)

Cardinal visible only	Lateral visible only

Edentulous (No developed teeth present)

Pallial sinus
Not sure


Deep (Extending beyond the midline)	Moderate (Extending over 1/3 of the shell but not beyond the midline)

Shallow (not extending beyond 1/3 of the shell)	Indistinct (Pallial line and sinus indistinct)

None present (Pallial line visible and complete)