Definitions
1.NounA northern horse mussel, any of species Modiolus modiolus of mussels of northern waters of Europe and the Atlantic and Pacific coasts of North America
2.NounAny in subfamily Modiolinae of mussels.
3.NounAtrina squamifera, of South Africa
4.NounAtrina zelandica, a large bivalve common from low tide to 45 m depth with a thin, dark, wedge-shaped shell covered with hollow spines.