n.1.(Zool.) The triangular space under the beak of many brachiopod shells.
Webster's Revised Unabridged Dictionary, published 1913 by G. & C. Merriam Co.
References in periodicals archive ?
Delthyrium in a form of isosceles triangle, covered by convex deltidium with large sealed foramen extending for about half of the deltidium height (Fig.
Delthyrium covered by deltidium. Foramen very minute, sealed and situated in the topmost part of deltidium.
106), and delthyrium covered by deltidium, all characteristic of the genus.