̷ ̷ˈ ̷ ̷dēəm noun
( plural deltid·ia -dēə)
Etymology: New Latin, from Greek delta + New Latin -idium
1. : a plate partly or wholly closing the delthyrium of certain brachiopods — called also pseudodeltidium
2. : a pair of plates not homologous with the pseudodeltidium that performs the same function in other brachiopods — called also deltidial plates