*Maractis rimicarivora*, a new genus and species of sea anemone (Cnidaria: Anthozoa: Actiniaria: Actinostolidae) from an Atlantic hydrothermal vent

Abstract

*Maractis rimicarivora* is a new genus and new species of medium-sized sea anemone (Actiniaria) from the TAG (Trans-Atlantic Geotraverse) hydrothermal vent fields (26°08.3'N, 44°49.6'W; 3650 m). The genus, which belongs to family Actinostolidae, is distinguished by the following combination of features: six pairs of complete mesenteries, mesenteries not arrayed according to the *Actinostola* rule, all mesenteries gametogenic, tentacles not thickened at the base, and no tentacular mastigophores. The species is distinguished by long, longitudinally-furrowed tentacles, and a roughened column. Anemones of this species encircle black smokers at distances from 15 to 60 m. This is the second species to be reported from hydrothermal vents of the Atlantic. Four species have been reported from Pacific hydrothermal vents.