Tilly bone

an unusually thickened bone which may occur in the axial or cranial skeleton of some fishes, e.g. thickenings of haemal and neural spines, postcleithra and anterior cranium in Lagocephalus. Named for Tilly Edinger of Harvard who studied these structures. Being larger and denser than usual bones, they are often found concentrated on beaches and in middens and, when rounded by wear and wave action, tend to look very unfish-like. Also called hyperostosis, q.v