deltidium
noun
del·tid·i·um
plural deltidia
-dēə
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
Word History
Etymology
New Latin, from Greek delta + New Latin -idium