| These are the drum-covers or opercula, from beneath which the sound issues. |
| The sporophytes also develop opercula, peristomes, continuous columella, and a spongy layer between the amphithecium and the spore mass. |
| I have already pointed out the few very trifling points, in which the opercula of the two species differ. |
| The opercula of multivalve shells are composed of two or four pieces, which are called the opercular valves. |
| It was shaped and ornamentally carved and painted to represent a wood-worm and inlaid along the rounded upper edge with opercula. |
| These fish do not have gills or opercula like most bony fishes. |
