SiphonobranchiataSi`pho*no*bran`chi*a"ta\, n. pl. [NL. See Siphon, and Branchia.] (Zo["o]l.) A tribe of gastropods having the mantle border, on one or both sides, prolonged in the form of a spout through which water enters the gill cavity. The shell itself is not always siphonostomatous in this group.