Cerastoderma glaucum, the lagoon cockle, is a species of saltwater clam, a marine bivalve mollusc in the family Cardiidae, the cockles. This species is found along the coasts of Europe and North Africa, including the Mediterranean and Black Seas and the Caspian Sea, and the low-salinity Baltic Sea. It is a euryhaline species living in salinities 4-100 ‰. In north-west Europe (including the British Isles), it typically does not live on open shores but rather in shallow burrows in saline lagoons, or sometimes on lower shores in estuaries. It cannot tolerate significant exposure to the air. The form found in lagoons is thinner-shelled than the estuarine populations.