Siphonata

‖n. pl. [ NL. ] (Zool.) A tribe of bivalve mollusks in which the posterior mantle border is prolonged into two tubes or siphons. Called also Siphoniata. See Siphon, 2 (a), and Quahaug. [ 1913 Webster ]

{ ‖‖‖ } n. pl. [ NL., fr. Gr. 'a priv. + &unr_; a tube. ] (Zool.) A group of bivalve mollusks destitute of siphons, as the oyster; the asiphonate mollusks. [ 1913 Webster ]