gill-flaps

Updated: May 7, 2025

The tendency of the whole affair to roll was partly corrected by a horizontal lateral fin on either side, and steering was chiefly effected by two vertical fins, which normally lay back like gill-flaps on either side of the head. It was indeed a most complete adaptation of the fish form to aerial conditions, the position of swimming bladder, eyes, and brain being, however, below instead of above.

H. G. (Herbert George) Wells - The War in the Air