clam: burrowing marine mollusk living on sand or mud; the shell closes with viselike firmness
bivalve: marine or freshwater mollusks having a soft body with platelike gills enclosed within two shells hinged together
cephalosporin: one of several broad spectrum antibiotic substances obtained from fungi and related to penicillin (trade names Mefoxin); addition of side chains has produced semisynthetic antibiotics with greater antibacterial activity