Variations of Indosphenia sowerbyi. a–c typical form from Adyar river d–e internal views of cleaned valves from Adyar river, pallial line false colour added d. f specimen with epifauna attached to posterior end, from Adyar river g–h specimen from Cooum river j internal showing blotched pattern on dry mantle tissue k posterior sculptured variety from Cooum river l–n Syntype of Sphenia sowerbyi from Ariancoupan, Pudicherry NHMUK 1893.3.16.6-7. Scale bar: 5 mm.