Protoconch II about 0.4 mm in length, which indicates a long planktonic larval stage with a high dispersal capability. The extremely enlarged gills contain sulphide oxidizing chemoautotrophic symbiotic bacteria. A commensal polychaete of the genus Branchipolynoe was encountered within the mantle cavity of most specimens. Mussels of the genus Gigantidas are found on warm seeps near active submarine volcanoes and therefore are included herein. The species lives in dense populations at sulphur-rich hydrothermal seepings, they are partly buried in sediment.