Webster’s Revised Unabridged Dictionary · 1913
Pygobranchia
Py′go·bran′chi·a, n. pl. [NL., fr. Gr. πuγή the rump + βράγχιον a gill.] (Zoöl.) A division of opisthobranchiate mollusks having the branchiæ in a wreath or group around the anal opening, as in the genus Doris.