Sub-Class IV.—Chondropterygii.

Skeleton cartilaginous; skull without sutures. Body with medial and paired fins, the hinder pair abdominal; caudal fin with produced upper lobe. Gills attached to the skin by the outer margin, with several intervening gill-openings; rarely one gill-opening only. No gill-cover. No air-bladder. Three series of valves in the bulbus arteriosus. Intestine with a spiral valve. Optic nerves commissurally united, not decussating. Ovaries with few and large ova, which are impregnated and, in some developed internally. Embryo with deciduous external gills. Males with prehensile organs attached to the ventral fins.