Examples from the Web for opercle
On our sunfish we see that the opercle ends behind in a long and narrow flap, which looks like an ear.
Overlying these is the system of membrane bones already mentioned, including the opercle or gill-cover.Elementary Zoology, Second Edition|Vernon L. Kellogg
In most of the higher fishes a small accessory gill (pseudobranchia) is developed in the skin of the inner side of the opercle.
The largest uppermost flat bone of the gill-covers is known as the opercle .
In Erpetoichthys only the opercle is distinct among the gill-covers.