Delthyris
Del*thy"ris\, n. [NL., fr. Gr. de`lta the name of the letter [Delta] + thy`ra door.] (Zo["o]l.) 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.