ID Keys
*Images in development


Robust shells with distinct, external, radial sculpture of riblets, ribs or plications, ctenolium present
Go to #2
Thin to fragile glassy shells if radial sculpture present then ctenolium absent (mostly deep water)
Go to #16
Valves equally convex
Go to #4
One valve flat, the other convex
Go to #3
14-17 well developed ribs
Pecten maximus
18-20 low weakly developed ribs (alien on stranded marine litter)
Euvola ziczac
Radial sculpture weak or very fine
Go to #5
Radial sculpture of distinct ribs or undulations
Go to #8
Shell with commarginal undulations and very fine radial striations (bathyal/abyssal)
Go to #6
Shell lacking commarginal undulations
Go to #7
Radial sculpture distinct, riblets present of the right valve ear (Atlantic Margin)
Hyalopecten pudicus
Radial sculpture weak, ears smooth (Arctic)
Hyalopecten frigidus
Sculpture the same on both valves, up to 50 smooth riblets, some shells becoming undulated.
Palliolum tigerinum
Sculpture on left valve stronger, up to 70 fine riblets bearing raised scales
Palliolum striatum
Radial sculpture plicate (undulations) with or without underlying radial riblets
Go to #9
Radial sculpture of ribs or riblets only
Go to #10
Ears almost equal in size, with or without underlying radial riblets
Pseudamussium peslutrae
Anterior ears much longer than posterior
Palliolum tigerinum
Sculpture of primary ribs and radial striations
Go to #11
Sculpture of primary ribs and secondary smaller riblets
Go to #14
Sculpture of 19-22 ribs, ears subequal
Go to #12
Sculpture of 25-35 narrow ribs bearing flattened spines, easrs very unequal
Go to #13
Ribs with radial striations
Aequipecten opercularis
Each rib bordered by a row of fine spines (alien on stranded litter)
Aequipecten heliacus
27-35 ribs, multi-coloured
Mimachlamys varia
41-48, white
Mimachlamys varia nivea
Disc elongate with up to 50 ribs of uneven size, becoming distorted and cemented after 10-20mm
Talochlamys pusio
Disc subcircular shell not distorted or cemented
Go to #15
Shell with distinct primary (c.15) and secondary ribs and riblets (to 45) shelf edge/ bathyal
Karnekampia sulcata
Primary and secondary ribles of similar size, to 140 in large shells (boreal/arctic)
Chlamys islandica
Ctenolium present
Go to #17
Ctenolium absent
Go to #18
Thin often brightly coloured with antimarginal microsculpure only (shelf)
Palliolum incomparabile
Glassy shells with antimarginal sculpture and commarginal rows of small vesicles (shelf edge/bathyal)
Delectopecten vitreus
With internal riblets
Go to #19
Lacking internal riblets
Go to #20
Exterior of left valve with narrow radial riblets
Parvamussium permirum
Exterior of left valve with commarginal lines only
Propeamussium lucidum
Radial rows of vesicles present on left valve
Cyclopecten hoskynsi
No radial macrosculpture
Go to #21
Commarginal ridges or undulations present
Go to #22
No commarginal sculpture
Go to #23
Commarginal ridges over whole valve
Cyclopecten ambiannulatus
Shell smooth except for few marginal undulations
Catillopecten eucymatus
No antimarginal microsculpture
Similipecten similis
Antimarginal sculpture present on at least part of a valve
Go to #24
Antimarginal sculpture over whole of left valve
Similipecten greenlandicus
Sparse antimarginal sculpture restricted to umbo of left valve
Similipecten oskarssoni