Protobranchia Pelseneer 1889

Key to genera and species of Protobranchia found on GB

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)