Indian Ocean, Sri Lanka, Tambalagam Bay (= Tambalagam Lake), centre of the lake (geocoordinates not provided, estimated with gazetteer to be approximately lat. 8.52º, long. 81.16º); fine black mud in oyster beds, 1-4 fathoms (1.8-7.3 m), in brackish water (11.0-19.0 p.p.t.)