ID Keys
*Images in development


Radial riblets on part or all of the body of the shell
Go to #2
Body of shell with commarginal sculpture only
Go to #6
Anterior with commarginal ridges abruptly separated from posterior ribbed area
Myonera demistriata
Radial riblets over the whole body, fading anteriorly
Go to #3
Rostrum short, body roundly quadrate, riblets absent from median area
Cardiomya cadiziana
Rostrum long, body oval, median area with riblets
Go to #4
With 20 primary radial riblets without or with few secondary riblets
Go to #5
With up to 65 primary and well developed secondary riblets
Cardiomya striata
Dorsal margin of rostrum concave (shelf-upper slope)
Cardiomya costellata
Dorsal margin of rostrum straight (abyssal)
Cardiomya knudseni
Rostrum very short, truncate
Go to #7
Rostrum short to very long, roundly pointed
Go to #9
Rostrum smooth with 2 weak radial keels

We have only examined the single valve collected by the Porcupine Expedition. It shows no sign of cardinal teeth so does not conform with the definition of
Pseudoneaera given by Poutiers & Bernard (1995).
Pseudoneara truncata
Rostrum wrinkled.
Go to #8
Weak anterior tooth in each valve.

Poutiers & Bernard (1995) recognise with reservations the following species recorded from the NE Atlantic,
P. atlantica, P. colpodes, P. ruginosa and P. verityi. We are unable to make definitive identifications within this group of species.
Protocuspidaria spp.
[Taxon under review]  
Posterior set off by a sharp angulate ridge, rostrum broad, rounded and lacking radial sculpture
Tropidomya abbreviata
Posterior not set off by a sharp angulate ridge
Go to #10
With accessory shelf supporting the posterior adductor in both valves, This is not part of the hinge and should not be confused with posterior lateral teeth
Go to #11
Hinge with or without lateral teeth, posterior adductor scar with no supporting shelf.
Go to #12
Body deep (H=L), rostrum very short, sulcus weak, sculpture on body of well defined commarginal very fine ridges.
Halonympha inflata
Body of shell ovate (L>H). rostrum short defined by change in sculpture, rostrum wrinkled, body with commarginal lines but appears smooth.
Halonympha depressa
Posterior roundly pointed, rostrum very short not defined ventrally, anterior of body with widely spaced commarginal ridges, hinge with a single posterior lateral in the RV
Cuspidaria undata
Rostrum well defined
Go to #13
Body with lamellar commarginal sculpture
Go to #14
Body with commarginal sculpture of incremental lines and growth stops only
Go to #15
Rostrum long, making posterior of shell longer than anterior, hinge lacking teeth
Myonera alleni
Rostrum moderately long shell equilateral, small posterior lateral in RV
Cuspidaria lamellosa
Hinge lacking teeth
Go to #16
Hinge with at least a single posterior lateral in the RV
Go to #17
Rostrum set off by a weak rounded ridge and with 2-3 faint radial ridges along the rostrum.

Myonera sulcifera is said to have a weak posterior cardinal in the RV but we cannot discern this in the Porcupine shells
Myonera sulcifera
Rostrum defined by a shallow sulcus only, overall minutely granular more prominent on rostrum
Myonera sp.
Hinge with anterior and posterior laterals in RV
Rhinoclama notabilis
Hinge with only a posterior lateral in RV
Go to #18
Rostrum proportionately very long, slightly longer than body
Cuspidaria rostrata
Rostrum not as long as body
Go to #19
With micro-punctate sculpture overall
Cuspidaria parva
With commarginal lines and growth stops only
Go to #20
Anterior slope long, almost straight
Cuspidaria cuspidata
Anterior broadly rounded
Go to #21
Body tumid, rostrum short somewhat upturned and twisted to one side
Cuspidaria subtorta
Rostrum not twisted to one side
Go to #22
Dorsal margin of rostrum sloping gently some slightly up-curved, anterior dorsal margin high (bathyal)
Cuspidaria obesa
Dorsal margin of rostrum sloping, anterior dorsal margin indistinct (arctic)
Cuspidaria glacialis