We present an emended diagnosis of Bitectatodinium spongium (Zonneveld, 1997) Zonneveld et Jurkschat, comb. nov. previously described as ?Algidasphaeridium spongium. New data from surface samples of the Pakistan shelf are combined with information from sediment traps off Somalia and Arabian Sea surface sediments to elucidate the taxonomy, ecological affinity and preservation of B. spongium. A pronounced relationship is detected between high concentrations of B. spongium and well-mixed, nutrient-rich surface waters, as observed in upwelling regions and in the vicinity of the Indus River outlet. High concentrations of this species are also found in coastal regions and regions with tropical sea surface temperature conditions. No relationship is observed between its distribution and differences in sea-surface salinity nor evidence for decay of B. spongium in relation to oxygen availability in bottom sediments. ... : Supplement to: Zonneveld, Karin A F; Jurkschat, Thomas (1999): Bitectatodinium spongium (Zonneveld, 1997) Zonneveld et Jurkschat, comb. nov. from modern sediments and sediment trap samples of the Arabian Sea (northwestern Indian Ocean): taxonomy and ecological affinity. Review of Palaeobotany and Palynology, 106(3-4), 153-169 ...