Source : Webster's Revised Unabridged Dictionary (1913)

Siphonobranchiata \Si`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.