Defn: Relating to, or like, a delta.
DELTHYRIS Del*thy"ris, n. Etym: [NL., fr. Gr. de`lta the name of the letter thy`ra door.] (Zoöl.)
Defn: 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.
DELTIC
Del"tic, a.
Defn: Deltaic.
DELTIDIUM
Del*tid"i*um, n. Etym: [NL., fr. Gr. de`lta, the letter (Zoöl.)
Defn: The triangular space under the beak of many brachiopod shells.
DELTOHEDRON
Del`to*he"dron, n. Etym: [Gr. de`lta, the letter 'e`dra seat, base.]
(Crystallog.)
Defn: A solid bounded by twelve quadrilateral faces. It is a hemihedral form of the isometric system, allied to the tetrahedron.
DELTOID Del"toid, a. Etym: [Gr. deltoeidh`s delta-shaped; de`lta the name of the letter ei^dos form: cf. F. deltoïde. See Delta.]