The Collaborative International Dictionary of English v.0.48:

Trichobranchia \Trich`o*bran"chi*a\, n. [NL., fr. Gr. tri`x,
   tricho`s, hair + branchia.] (Zool.)
   The gill of a crustacean in which the branchial filaments are
   slender and cylindrical, as in the crawfishes.
   [1913 Webster]