Cercariae and metacercariae of the acanthocolpid trematode, Stephanostomum cloacum (Srivastava, 1938) are described and illustrated, based on material collected from Chilka Lake, a brackish water lagoon. Natural infections with the cercariae were found in the snail, Nassarius orissaensis and with the metacercariae in the bivalve, Modiolus undulatus. Cercariae are distomate, ophthalmoxiphidiocercous, and possess a small stylet, simple tail, four pairs of penetration glands arranged in two groups and a large granular excretory bladder. Development of the cercaria into the metacercaria was followed in M. undulatus under laboratory conditions. Infections with adults of S. cloacum were identified in the fish Triacanthus biaculeatus, found in the lake.