The geographic distributions of most surface-dwelling species of planktonic Foraminifera are now well-known (Bé, 1959, 1960, 1977; Bé & Hamlin, 1967; Bé, Vilks & Lott, 1971; Bé & Tolderlund, 1971; Tolderlund & Bé, 1971; Bé & Hutson, 1977). These distributions, established from species abundance in plankton net collections, have been used to correlate abundance with physical and chemical variables (primarily temperature and salinity) in an effort to establish the factors which control the geographic range of these shelled protists. Significant correlations have been derived from these comparisons and the temperature and salinity ‘limits’ and ‘optima’ of a number of species have been reported (e.g. Bé & Tolderlund, 1971).