ID Keys


Shell height greater than length, subcircular to triangular [c1, c2, c3], ligament internal in an anteriorly directed (opisthodetic) chondrophore = Nuculoidea & Pristiglomoidea
Go to #2
Shell longer than high, frequently subrostrate or rostrate [c4, c5, c6], ligament internal in a shallow resilifer or external = Nuculanoidea
Go to #14
Shell subcircular or obliquely oval, hinge with few teeth subparallel to hinge plate [c7] = Pristiglomoidea
Go to #3
Shell triangular to subovate, hinge with numerous, prominent erect teeth [c8] = Nuculoidea
Go to #4
Shell obliquely oval [c9]
Pristigloma alba
Shell subcircular [c10]
Pristigloma nitens
Internal margin denticulate [c11]
Go to #5
Internal margin smooth [c12]
Go to #10
Shell triangular or subtriangular [c13]
Go to #6
Shell subovate [c14], prominent larval shell, cancellate sculpture (abyssal)
Nucula atacellana
Triangular, distinctly higher than long, marked decussate sculpture, commarginal ridges becoming stronger towards margin. (bathyal)
Nucula tumidula
Subtriangular, anterior slope much longer and more gentle than posterior. (shelf)
Go to #7
Sculpture distinctly decussate, lunule with transverse corrugations, periostracum netted
Nucula sulcata
Sculpture fine, lunule smooth, periostracum smooth
Go to #8
Periostracum shiny
Nucula nitidosa
Periostracum matt
Go to #9
Shell height 85% of length, periostracum uniformly coloured shades of olive
Nucula nucleus
Shell height 80% of length, periostracum often with coloured rays
Nucula hanleyi
Shells distinctly higher than long, triangular or rhomboidal
Go to #11
Shells longer than high subtriangular or subovate
Go to #12
Shell triangular anterior and posterior equally inclined (abyssal)
Brevinucula verrilli
Shell rhomboidal, umbos inflated (upper slope, northern)
Ennucula corticata
Shell subovate, posterior truncated, surface microscopically granular (bathyal)
Ennucula granulosa
Shell subtriangular or subovate, posterior acute
Go to #13
Shell subtriangular, anterior slope long, almost straight (shelf)
Ennucula tenuis
Shell subovate, anterior slope curving (bathyal)
Ennucula corbuloides
Hinge teeth few, elongate, subparallel with hinge plate
Go to #15
Hinge teeth pointed erect
Go to #16
Shell cylindrical
Silicula fragilis
Shells subrostrate with a posterior ventral sinus
Go to #17
Shells rostrate or subovate to oval
Go to #22
Shells with a sharply pointed dorsally situated posterior beak, ligament both interior and exterior, gut loop multi-coiled
Go to #18
Shells with a pointed, medially or downwardly angled posterior beak, ligament interior, gut loop simple or multi-coiled
Go to #19
Posterior much deeper than anterior, posterior below rostrum bulging
Bathyspinula subexcisa
Posterior a little deeper than anterior, sulcus below rostrum weak
Bathyspinula filatovae
Rostrum blunt
Go to #20
Rostrum acute
Go to #21
Shell thick becoming tumid, sculpture of fine co-marginal ridges
Ledella ultima
Shells normal thickness, sculpture of weak radial and co-marginal ridges, periostracum pustulose
Ledella pustulosa
Posterior dorsal margin sloping (bathyal)
Ledella messanensis
Posterior dorsal margin almost horizontal, dorsal margins sunken close to umbos. (Arctic shelf)
Portlandia arctica
Minute (<1.5mm), rounded tumid shells
Go to #23
Shells ovate to rostrate
Go to #25
Outline elliptical
Go to #24
Outline subcircular (southern, bathyal)
Microgloma tumidula
Shell smooth, teeth obscure
Microgloma guilonardi
Shell with commarginal ridges at margins, teeth prominent
Microgloma pusilla
External ligament visible close to beaks
Go to #26
Ligament internal not visible in joined valves
Go to #28
Shell oblong, posterior broad, roundly truncated
Malletia johnsoni
Shell subovate to elliptical, posterior pointed
Go to #27
Subovate, robust shells with commarginal ridges
Neilonella latior
Elliptical, fragile smooth shells
Katadesmia cuneata
Robust narrowly rostrate shells with prominent commarginal sculpture
Go to #29
Thin shells with weak sculpture, subovate to oblong
Go to #31
Elongate shells, rostrum blunt
Go to #30
Oval shell, rostrum acutely pointed
Saccella commutata
Commarginal ridges strong across whole shell
Nuculana minuta
Commarginal ridges weak posteriorly, strongest on anterior
Nuculana pernula
Large, subelliptical shell (arctic/subarctic outer shelf)
Yoldia hyperborea
Shells rarely exceeding 10mm, subovate to oblong