The Collaborative International Dictionary of English v.0.48:

Siphonata \Si`pho*na"ta\, 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]