SERICOSURA HETEROSCELA AND S-CYRTOMA, NEW SPECIES, AND OTHER PYCNOGONIDA FROM ATLANTIC AND PACIFIC HYDROTHERMAL VENTS, WITH NOTES ON HABITAT AND ENVIRONMENT

The first new hydrothermal vent pycnogonid from the Mid-Atlantic Ridge , Sericosura heteroscela, new species, is described and illustrated fr om specimens taken in 1727 m south of the Azores and other nearby loca lities in similar depths from vent areas just west of the azores, Male s of this new species have extremely dimorphic anterior and posterior propodi. Another new species, S. cyrtoma, is described and figured fro m a hydrothermal vent at 13 degrees N off the Pacific coast of Mexico, in 2563 m. A juvenile specimen of a possibly new third Sericosura spe cies is discussed and compared with S. venticola Child. The specimen w as taken from vents north of Easter island, southeast Pacific, in 2578 m. The three species are compared with each other and with other know n hydrothermal vent species in this genus, their distribution is discu ssed, and a Sericosura key is presented. Two known species in the gene ra Callipallene and Colossendeis are also listed from the same Mid-Atl antic vent areas. Descriptive remarks on the habitat and environment o f the specimens are presented.