Category:Opisthobranchia

O*pis`tho*bran"chi*a, o*pis`tho*bran`chi*a"ta, n. pl. Etym: [nl., From gr. (zoöl.)

Defn: a division of gastropod mollusca, in which the breathing organs Are usually situated behind the heart. It includes the tectibranchs And nudibranchs.