PROCEEDINGS OF THE BIOLOGICAL SOCIETY OF WASfflNGTON 109(2):248-255. 1996. A new genus and species of ampharetid polychaete from deep-sea hydrothermal vent community in the Azores triple-junction area Daniel Desbruyeres and Lucien Laubier (DD) Departement Environnement Profond, Centre de Brest de I'lFREMER, B.P. 70, 29280 Plouzane, France; (LL) Laboratoire de Physiologic dcs Etrcs marins, Institut Oceanographique, 195 rue Saint Jacques, 75005 Paris, France Abstract. — Amathys lutzi, a new genus and species of Ampharetinae (Poly-chaeta: Ampharetidae), is described from active hydrothermal vents on the Lucky Strike segment, close to the Azores triple-junction area of the Mid-Atlantic Ridge. It is found in the same micro-habitat than Amphisamytha gal-apagensis Zottoli, 1983. It differs from all previously known Ampharetinae by the number (17) of thoracic uncinigerous segments. In 1993, the Lucky Strike expedition (cruise Atlantis II 129-6) visited an active hydrothermal field situated at 37°17.538'N and 32° 1 6.490' W in 1626 m. The expedi-tion consisted of six dives of the DSRV Al-vin and aimed to find and describe active hydrothermal sites and the biological com-munities associated with venting areas. Based on this first exploration, the Diva 2 expedition (1994) completed 24 dives of the submersible Nautile on the same hydro-thermal area. Hydrothermal activity occurs around a lava lake situated in the depression between three cones which form the sum-mit of a seamount, at the center of a long broad ridge segment that extends from 37°00'N to 37°35'N; hydrothermal activity includes flanges with pool temperature <200°C to black smokers venting fluids as hot as 333°C (Langmuir et al., 1993, pers. obs.). The dominant organisms in these hy-drothermal fields are populations of a new species of mussel (bathymodiolid) that col-onizes hydrothermal sulfide edifices and their vicinity. Other less conspicuous com-ponents of the fauna include new species of alvinocarid shrimps, peracaridan crusta-ceans, bythograeid crabs, sea-urchins and several species of polychaetes including a polynoid commensal of mussels (Van Do-ver et al. 1993). Ampharetid polychaetes were sorted from mussel washings, or found in tubes attached to mussel shell hinges and to sulfide or basaltic rocks. Materials and Methods The specimens were collected using Al-vin and Nautile manipulators. The samples were brought to the surface inside insulated boxes and were washed and sieved through a 250-|JLm mesh. They were sorted partially aboard the mother-vessels, then fixed in buffered formalin and preserved in 80% ethanol after a one day fixation. In the lab-oratory, specimens are dehydrated to ethyl alcohol absolute, critical point dried, put on stubs and coated with gold. Finally, the specimens were examined using a Philips XL 30 scanning electron microscope. Order Terebellida Family Ampharetidae Malmgren, 1865 Subfamily Ampharetinae Chamberlin, 1919 Amathys, new genus Diagnosis. — Thorax with 20 setigerous segments, of which the last 17 are uncini-gerous. Abdomen tapering rapidly with 16-20 uncinigerous segments, no notopodial or
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