CHÆTODON, in ichthyology, a genus of fishes belonging to the order of thoraci. The teeth are very numerous, thick, færaceous, and flexible: The rays of the gills are six. The back-fin and the fin at the anus are fleshy and squamous. There are twenty-three species, distinguished from each other principally by the figure of the tail, and the number of spines in the back-fin.