ID Keys
*Images in development

Ostreoidea, Chamoidea & Anomioidea

Lower valve not cemented to substrate but with a byssus foramen
Go to #2
One valve cemented to substrate
Go to #7
Upper valve with 3 muscle scars
Anomia ephippium
Upper valve with two scars separate or partially joined
Go to #3
Muscle scars smooth, upper valve often strongly sculptured ribbed with erect scales (aculeate). Gill with unreflected filaments
Heteranomia squamula
Muscle scars furrowed, Upper valve never aculeate, Gills with reflected filaments
Go to #4
Upper valve with radial ribs and or riblets
Go to #5
Upper valve smooth or with a fine cancellate but radially sinuous sculpture
Go to #6
Upper valve with prominent radial ribs and riblets, muscle scars joined or separate
Pododesmus patelliformis
Upper valve with fine wavy radial striations, muscle scars joined separated by a longitudinal ridge (alien on marine litter)
Pododesmus sp.
Upper valve finely cancellate but radially sinuous
Pododesmus squama
Upper valve smooth (alien on marine litter)
Pododesmus rudis
Both adductor muscles present, hinge with true teeth, (aliens on marine litter)
Go to #8
Single subcentrally situated adductor muscle scar
Go to #9
Shell white, uneven flattened scales
Chama congregata
Shell tinged pink, commarginal frills and fluted spines
Chama sarda
Muscle scar circular-subcircular, honeycomb (vesicular) shell structure present, marginal vermicular chomata present. (deep water)
Go to #10
Muscle scar crescentric, chomata if present nodular (ostreiine), vesicular shell layer absent
Go to #11
Muscle scar very round
Neopycnodonte zibrowii
Muscle scar oval
Neopycnodonte cochlear
Ovate shell with a prominent median longitudinal ridge (alien on marine litter)
Dendrostrea frons
Subcircular to ovate shells, some with plicate margin but lacking a raised longitudinal ridge
Go to #12
Ligulate (tongue shaped) in outline, lower valve deeply cupped with strong marginal plications, muscle scar darkly coloured, chomata absent
Crassostrea gigas
Subcircular to irregulary subcircular in outline, marginal plications weak, muscle scar not darkly coloured, ostreiine chomata present on at least the dorsal margins
Go to #13
With strong marginal chomata on most of the margin. Upper valve frondose rather irregular in outline. (alien on marine litter)
Ostrea equestris
Marginal chomata close to dorsal margins only, shells roughly circular, exterior scaly
Go to #14
Shells becoming black with paler radial rays (Menai Straits only)
Tiostrea chilensis
Shells beige to greyish
Ostrea edulis