ceras

ceras (noun; plural cerata; Greek keras, horn): 1. A horn or horn-like appendage.

2. (Mollusca: Gastropoda) In some Nudibranchia, numerous projections that act as gills on the dorsal body surface, may be club shaped or grapelike and usually brilliantly colored in red, yellow, orange, blue, green, or a combination of colors; functioning in respiration, containing blood from the hemocoel and tubular branches of the digestive gland.