Seventeen species in the seventeen genera of selachians are described from the early Middle Miocene Bihoku Group in Shobara area，Hiroshima Prefecture，southwest Japan．Based on the association of several dominant species，Carcharhinus-Isurus-Carcharias assemblage is recognized．The paleoecologic character of the assemblage is inferred as coastal，warm temperate waters based on habitat of living selachian genera and other fossils associated with selachian in record．