[gastropod] Polybranchia is a genus of sacoglossan sea slugs, shell-less marine opisthobranch gastropod mollusks in the family Caliphyllidae. == Species == Species within the genus Polybranchia include: ...
• (n. pl.) A division of Nudibranchiata including those which have numerous branchiae on the back.
Pol`y·bran'chi·a noun plural [ New Latin See Poly- , and Branchia .] (Zoology) A division of Nudibranchiata including those which have numerous branchiæ on the back.