I have already pointed out the few very trifling points, in which the opercula of the two species differ.
It should be mentioned that the Serpulacea are provided with opercula.
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 are the drum-covers or opercula, from beneath which the sound issues.
The opercula vary to a great extent in the different genera; in some cases they are calcareous, in others cartilaginous.
Two other genera of land shells are provided with opercula, and consequently might be confounded with this genus.
The opercula of various shells differ in the first place as to their chemical composition.
The figures represent some of the commoner types of opercula.
The third section contains the following genera of land shells with opercula.
operculum o·per·cu·lum (ō-pûr'kyə-ləm)
n. pl. o·per·cu·lums or o·per·cu·la (-lə)
Something resembling a lid or cover.
The portions of the frontal, parietal, and temporal lobes covering the insula.
The mucus sealing the endocervical canal of the uterus after conception.
The attached flap in cases of torn retinal detachment.
The mucosal flap partially or completely covering an unerupted tooth.