Bathymodiolus (Bivalvia: Mytilidae) from hydrothermal vents on the Azores Triple Junction and the Logatchev Hydrothermal Field, Mid-Atlantic Ridge

Bathymodiolus azoricus n. sp. is described from the Lucky Strike (31°17'N) and the Menez Gwen (37°50'N) hydrothermal fields on the Azores Triple Junction, Mid-Atlantic Ridge, and another species, Bathymodiolus sp.aff.B. puteoserpentis from Logatchev (14°45'N) hydrothermal field is treated but not named.Both species are compared with B. puteoserpentis Cosel, Métivier & Hashimoto, 1994, from the Snake Pit area (23°22'N), also on the Mid Atlantic Ridge.B. azoricus is very variable but well distinguished from Bathymodiolus sp. and B. puteoserpentis by its almost terminal umbo.The three species differ from the type species B. thermophilus principally by the absence of an inner mantle fusion and a very short valvular siphonal membrane.The slight differences between B. puteoserpentis and Bathymodiolus sp. from the Logatchev field do not warrant separation of the latter on species level.The specific endemism of Mytilidae along the Mid-Atlantic Ridge is discussed.R.von