p. 133 - 143 RELATIVE NUMERIC IMPORTANCE OF TWO DIFFERENT SOFT-BOTTOM BENTHIC GROUPS (MOLLUSCS AND CRUSTACEANS) IN THE SOUTHERN BLACK SEA E. Mutlu and M. Unsal Institute of Marine Sciences, Erdemli, ICEL, Turkey Abstract Single bulk sediments were separately collected with a Van Veen grab from 20 stations along the Turkish coast of the Black Sea in September 1988 and in January 1989. The numeric indices converted from these samples pronounced that molluscs and crustaceans were distributed in the equal frequency of occurrence while molluscs contributed highly much biomass (99%) and abundance (69%), mainly with a few certain species such as Modiolus phaseolinus, Mytilus galloprovincialis. Crustaceans were considered to be relatively contributors (0.1% biomass, 30% abundance), with small size organisms such as Synisoma capito, Iphinoe elisae and Cythereis antiquata.