The Collaborative International Dictionary of English v.0.48:

Siphonobranchiate \Si`pho*no*bran"chi*ate\, a. (Zool.)
   Having a siphon, or siphons, to convey water to the gills;
   belonging or pertaining to the Siphonobranchiata. -- n. One
   of the Siphonobranchiata.
   [1913 Webster]