The Conchoecia skogsbergi species complex (Ostracoda, Halocyprididae) in the Atlantic Ocean A. J. Gooday Institute of Oceanographic Sciences, Wormley, Godalming, Surrey, U.K. Introduction The planktonic ostracod genus Conchoecia includes a heterogeneous array of 105 described species with at least another 15-20 recognized, but as yet undescribed (Angel, personal communication). The named species have been separated into a number of groupings (Miiller, 1 906# ; Skogsberg, 1 920). Some of these were given generic status by Granata & di Caporiacco (1949) and Poulsen (1973) but this nomenclature is not universally accepted because several of the genera appear to be unnatural units (Angel and Fasham, 1975 : 71 1). One of the more important, and probably natural, assemblages is the rotundata group ( = Metaconchoecia Granata & di Caporiacco, 1949), which comprises 11 or 12 previously described species, most obviously united by the location of the left asymmetric gland in an anterior position, just behind the rostrum. Although most of the rotundata group species are fairly well understood, two names, C. rotundata Miiller, 1890 and C. skogsbergi lies, 1953, have not been applied consistently. C. rotundata has been the subject of particular confusion. These long standing taxonomic problems have been compounded in recent years by Angel's recognition that 'C. rotundata' in Atlantic Discovery material comprises an array of very similar 'forms' (Angel, 1972; 1979 : 68-73; Angel & Fasham, 1975 : 71 1). In the present paper, which is largely based on the same Discovery material, C. rotundata and C. skogsbergi are redescribed and eight new species are established. All but one of these ten species are embraced by Angel's 'C. rotundata forms 1-15'. They together make up a closely related assemblage within the rotundata group which is referred to here as the skogsbergi complex. It is obvious from material in other collections that many, perhaps all, of the skogsbergi complex species were seen by earlier workers. Understandably, they were usually identified as C. rotundata or, in more recent literature, as C. skogsbergi. Materials and methods Most of the material was collected by the RRS Discovery between 1968 and 1974 in the N. Atlantic at a series of stations situated approximately along the 20W meridian between 60N and the equator (Angel & Fasham, 1975) and also along a 32N transect from Africa to Bermuda (Angel, 1979). With a few exceptions, these samples were taken with the RMT 1 component of the RMT 1 + 8 opening and closing net system which is able to sample discrete horizontal horizons within the water column (Baker, Clarke & Harris, 1973). The gear was usually fished at four depth horizons down to 100 m, then 100 m horizons down to 1000 m and broader bands between 1000 m and 2000 m, thus allowing reasonably precise data on the depth distribution of planktonic organisms to be obtained. Further details of sampling procedures with the RMT 1 +8 are given elsewhere (Angel & Fasham, 1976; Badcock & Merrett, 1976; Angel, 1979). At Discovery Station 6665, a modified Indian Ocean Standard Net (Nl 13) fitted with a catch dividing bucket (CDB, Foxton, 1963) was used. A smaller number of specimens from the S. Atlantic and the Atlantic sector of the Southern Ocean Bull. Br. Mus. nat. Hist. (Zool.) 40 (4) : 1 37-209 Issued 30 July 1 98 1
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