Scanning electron micrographs of hinges of myids and Potamocorbula. Left hand series are right valves, left hand series are left valves with the chondrophore viewed from above. a Mya arenaria b Mya truncata c Sphenia binghami d Indosphenia kayalum e Potamocorbula amurensis. Scale bar: 500 µm. Abbreviations: as, anterior socket. at, anterior tooth. fl, posterior flange. lg, ligament plate. ps, posterior socket. pst, pseudotooth. r, ridge. rs, resilifer.