Thyasira polygona (Jeffreys) (Bivalvia: Lucinoidea), an abandoned taxon with a possible amphi Atlantic distribution

Thyasira polygona (Jeffreys) previously regarded as a variety of T. flexuosa (Montagu) is considered to be a distinct species. It is confirmed from British waters on the west of Scotland and the North Sea. Similar taxa have been recorded from the Mediterranean [Ptychina biplicata Philippi], Caribbean [T. trisinuata (d'Orbigny)] and north-western Atlantic [T. obesa (Verrill)] but shell and anatomical study is required to confirm the relationships of these. It is surmised that the British and northwestern Atlantic material is conspecific and represents an additional amphi-Atlantic Thyasira species.