BRANCHIOSTEGAL MEMBRANE
branchiostegal membrane: translation
the membrane below the operculum, often attached to the isthmus, supported by branchiostegals and helping to enclose the gill chamber ventrolaterally. Branchiostegal membranes are separate when the membranes of the two sides are separate from one another and the isthmus; they are united and free from the isthmus when the membranes of the two sides are joined to one another and have a narrow or wide margin behind unattached to the isthmus; and are joined to the isthmus when they fuse to the isthmus without a free margin. Often inappropriately called the gill membrane