The Collaborative International Dictionary of English v.0.48:

Sertularia \Ser`tu*la"ri*a\, n. [NL., dim. fr. L. serta a
   garland.] (Zool.)
   A genus of delicate branching hydroids having small sessile
   hydrothecae along the sides of the branches.
   [1913 Webster]

WordNet (r) 3.0 (2006):

Sertularia
    n 1: sessile hydroid that forms feathery colonies [syn:
         Sertularia, genus Sertularia]