The Collaborative International Dictionary of English v.0.48:

Syngnathi \Syng"na*thi\, n. pl. [NL., fr. Gr. sy`n with + ?
   jaw.] (Zool.)
   A suborder of lophobranch fishes which have an elongated
   snout and lack the ventral and first dorsal fins. The
   pipefishes and sea horses are examples. -- Syng"na*thous,
   a.
   [1913 Webster]