‖Del‐thy″ris (?), n. [NL., fr. Gr. δέλτα the name of the letter Δ + θύρα door.] (Zoöl.) A name formerly given to certain Silurian brachiopod shells of the genus Spirifer.
Delthyris limestone(Geol.), one of the divisions of the Upper Silurian rocks in New York.