See also Killeen & Turner (2009) for identification of many North Atlantic Yoldiella Verrill & Bush, 1897 and Ledella Verrill & Bush, 1897 species not found in the present material.
1. Hinge plate narrowing but not interrupted under the umbo, with teeth forming a continuous series........................................................................................................................................................... 2
– Hinge plate interrupted beneath the umbo by a ligamental pit......................................................... 3
2. Outline regularly oval, longer than high................... Tindaria sericea (Jeffreys, 1876) (Fig. 31G‒I)
– Outline rounded anteriorly and tapering posteriorly........................................................................................................................................ Pseudoneilonella latior (Jeffreys, 1876) [not found on GB]
3. Outline triangular with rounded ends; inside of shell nacreous....................................................... 4
– Outline rounded, oval, or with anterior end rounded and posterior end tapering; inside of shell not nacreous........................................................................................................................................... 6
4. Ventral margin smooth................................. Ennucula corbuloide s (Seguenza, 1877) (Fig. 31E‒F)
‒ Ventral margin crenulated by the termination of internal rods......................................................... 5
5. Shell plump, externally with fine radial microsculpture..................................................................................................................................................... Nucula atacellana Schenck, 1939 (Fig. 31C‒D)
– Shell rather compressed, sculpture mostly commarginal................................................................... ..................................................................................... Nucula tumidula Malm, 1861 (Fig. 31A‒B)
6. Posterior end acute or more or less angular...................................................................................... 7
– Posterior end rounded, even if somewhat tapering........................................................................... 8
7. Posterior end acute, umbo anterior to vertical midline.................................................................................................................................................. Ledella messanensis (Jeffreys, 1870) (Fig. 32A‒B)
– Posterior end bluntly angular, umbo posterior to vertical midline........................................................................................................................................... Ledella cf. orixa (Dall, 1927) (Fig. 32C‒D)
8. Shell less than 2 mm, white, rounded in outline........................................................................................................................................................... Pristigloma minima (Seguenza, 1877) (Fig. 31J‒K)
– Shell larger, definitely longer than high............................................................................................ 9
9. Shell inflated, posteriorly tapering.................... Yoldiella semistriata (Jeffreys, 1879) (Fig. 32G‒H)
– Shell very compressed, posterior part broadly rounded............................................................................................................................... Yoldiella valorousae Killeen & J. A. Turner, 2009 (Fig. 32I‒J)
Family Nuculanidae H. & A. Adams, 1858