anthobranchia

from The Century Dictionary.

• A suborder of nudibranchiate gastropods, with the branchiæ arranged in a rosette about the anus, whence the name. It includes the family Dorididæ and related forms. Also called Pygobranchia.

from the GNU version of the Collaborative International Dictionary of English.

• noun plural (Zoöl.) A division of nudibranchiate Mollusca, in which the gills form a wreath or cluster upon the posterior part of the back. See nudibranchiata, and Doris.