Corydoras panda the entire fin area. The caudal peduncle is marked with a black band, this black band encircling the caudal peduncle from dorsal to ventral surface. The adipose fin, supported by a small fin spine, sometimes contains black pigmentation. The head is the same ground colour as the body, with a black mask surrounding the eyes, descending vertically from the fontanel, over each eye, and ending in a triangular wedge immediately before the ventral surface of the head. The pectoral fins are positioned immediately behind the operculum, and are usually oriented horizontally when the fish is at rest, extended in a
Avicularium shape as the autozooids. Interzooidal avicularia are wedged between autozooids but do not replace an autozooid. Adventitious avicularia are placed somewhere on the external (frontal) wall of an autozooid and are usually much smaller. The 'birds-head' avicularium (e.g. "Bugula") is elevated above the colony by a stalk (peduncle). A zooid where the operculum is modified into a very long, hair-like structure is called a vibraculum. The cylcostome family Eleidae, which convergently evolved an opercular structure during the Early Cretaceous to Paleocene, also possess avicularia-like zooids. Avicularium The avicularium (pl. avicularia) in cheilostome bryozoans is a modified, non-feeding zooid. The operculum,