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Get access Abstract A study of modern pelagic subarctic Pacific phytoplankton has revealed the presence of three distinct species of Proboscia Sundstrom, including the type species P. alata and two new species with historical complications. P. subarctica (= Rhizosolenia alata f. curvirostris Gran) is markedly different in proboscis and valve morphology from the type species and in fact bears more resemblance to fossil members of the genus. P. eumorpha (= R. obtusa Hensen sensu Ostenfeld) resembles the austral species P. inermis, but may be distinguished easily from it by its more elongate proboscis and its less truncate valve shape. SEM observations and taxonomic discussions on both these new species are presented. Samples derived from time-series sediment traps, deployed in this region (September 1982-August 1986), have revealed strong temporal flux variations. P. alata flux represents summer-fall maxima, whereas P. subarctica is highest during spring followed by a gradual decrease towards winter.