Ceras, plural Cerata, are anatomical structures found externally in nudibranch sea slugs, especially in aeolid nudibranchs, marine opisthobranch gastropod mollusks in the clade Aeolidida. The singular of cerata is ceras, which comes from the Greek word `κέρας`, meaning `horn`, a reference to the shape of these structures. Cerata are dorsa...