The Collaborative International Dictionary
Pygobranchia
Pygobranchia \Py`go*bran"chi*a\, n. pl. [NL., fr. Gr. pugh` the rump + ? a gill.] (Zo["o]l.) A division of opisthobranchiate mollusks having the branchi[ae] in a wreath or group around the anal opening, as in the genus Doris.