EntityQ3519023· pop 9· linked from 311 articlestestSign in to savehard shell of some spherical marine animals, notably sea urchins and microorganisms such as testate foraminiferans, radiolarians, and testate amoebaeConnectionsForaminiferaEntityboneEntityTestudinesEntityInternational Standard Book NumberEntityAdriatic SeaEntityMolluscaEntityskeletonEntityseedEntityskullEntityprotistEntityisotopeEntityfossilEntitydigital object identifierEntityInternational Standard Serial NumberEntityEchinoideaEntitycelluloseEntityCephalopodEntitycrystallographyEntitycalcium carbonateEntityPhanerozoicEntityCategoriesMarine biologyMollusc shellsSea urchins