Benthic environmental assessments associated with oil and gas explorations along the UK Atlantic Margin have revealed deficiencies in the taxonomy of many deep-water taxa. Amongst the Bivalvia the protobranch genera Yoldiella and Portlandia are particularly complex. This study presents tabular keys, shell and gut loop descriptions for those taxa living on the continental slope and abyssal areas of the Atlantic Margin west and north of Scotland.
The study is based primarily on samples collected in three surveys under the direction of the Atlantic Frontier Environmental Network (AFEN) between 1996 and 2000, with additional material from museum collections. Specimens were found at 239 stations from depths ranging from 98 m. on the outer continental shelf to 2046 m. in Rockall Trough. One species of Portlandia and eight species of Yoldiella were recognized in the AFEN material P. intermedia, Y. annenkovae, Y. curta, Y. jeffreysi, Y. lucida, Y. nana, Y. philippiana, Y. propinqua and Y. valorousae nom. nov.
Yoldiella annenkovae is recorded for the first time in British or Irish waters.
Yoldiella valorousae nom. nov. is a replacement name for Y. lata sensu Allen, Sanders & Hannah 1995.
A further 8 species that occur in parts of the NE Atlantic adjacent to the AFEN study area are included. Y. biscayensis, Y. fabula, Y. frigida, Y. incala, Y. insculpta, Y. lenticula, Y. solidula, Y. thaerella sp. nov.
Y. thaerella sp. nov. is Y. inconspicua inconspicua sensu Allen, Sanders & Hannah 1995 non Y. inconspicua Verrill & Bush, 1898.
Y. incala is a taxon raised to species rank from Y. obesa incala Allen, Sanders & Hannah 1995.