DELTHYRIUM
delthyrium: translation
n.; pl. -ria [Gr. 4th letter, delta; thyrion, door]
(BRACHIOPODA)
The central triangular notch in the ventral valve, open to the hinge line; facilitating the passage of the pedicle; usually closed off from the hinge plate by the deltidium; delthyrial a; see notothyrium.