In the argument thus far we have considered terrestrial, adult amphibians, since it is only in these that either the normal middle ear and tympanum, or the opercular apparatus, is present.
The principal opercularbone or operculum of fishes.
Any one of the bony plates which support the gill covers of fishes; an opercular bone.
The principal opercular bone in the upper and posterior part of the gill cover.
A well-marked groove is present between the mandibular and opercular arches, but so far as we can make out it is not a remnant of the hyomandibular cleft.
Many of them have an accessory organ of respiration, in the form of an opercular gill, which is distinct from the pseudobranch, and can be present together with the latter; many also have spiracles like Elasmobranchii.
Behind this is placed the very conspicuous hyoid arch with its rudimentary opercular flap; and in the depression, partly covered over by the latter, may be seen a ridge, the external indication of the first branchial arch.
The opercular flap is larger, and the branchial arches behind it (two of which may be made out without dissection) are more prominent.
Defn: Any one of the bony plates which support the gill covers of fishes; an opercular bone.
Defn: The principal opercular bone or operculum of fishes.
The long-eared pondfish (Lepomis auritus) of the Eastern United States is distinguished by its very long opercular flap.
The posterior border of the hyoid arch is prolonged into an opercular fold.
A small opercular fold, developed from the lower part of the hyoid arch, covers over the bases of the gills.
Later stages after the enclosure of the gills by the opercular membrane.
The opercular flap attached to the hyoid arch is usually supported by a series of membrane bones, which attain their highest development in the Teleostei.
More advanced larva, in which the opercular fold has nearly covered the branchiae.
The hyoid arch is prolonged backwards into a considerable opercular fold, which to a great extent overshadows the branchial clefts behind.
The fore-limbs are not hidden beneath the opercular fold.
Shortly after hatching, there grows out from the hyoid arch on each side an opercular fold of skin, which gradually covers over the posterior branchial arches and the external gills (fig.
The sub-operculum is minutely crenulated on the edge, and has a small sub-membranous tip, which projects a little beyond the three opercular teeth.
The temples before the upper limb of the preoperculum are densely scaly, as is also the gill flap above the upper opercular ridge.
The opercular spines are as usual two in number, being the tips of two low even divergent ridges, with a curved notch in the edges of the bone between them.
I have never seen the opercular piece, or valve, as it is called by those conchologists who regard the Rudistes as bivalve mollusca.
Upper side of the opercular valve, showing a reticulated structure in those parts, b, where the external coating is worn off.
The atrium is thus analogous to the opercular cavity of fishes and tadpoles, and, as stated above, remains in communication with the exterior by means of the atriopore.
Verruca Stroemia, (with left hand scutum and tergum fixed), with the valves and compartments separated from each other; the homologous parts of the opercular valves are marked by corresponding letters and dashes.
O, O, opercular membrane, connecting the opercular valves with the overhanging basal edge of the sheath.
The opercular valves are not described, and I doubt whether the species could be recognised.
The little bristles above alluded to, which arise from the slips of membrane left adherent on the opercular valves, sheath, and walls, stand in rows; a row corresponding to each period of exuviation of the opercular membrane.
It appears that specimens with the left side uppermost, and therefore with the left opercular valves moveable, are considerably more common than those with the right valves moveable.
This circumstance, and their feebleness, is easily accounted for by the thick unyielding nature of the opercular membrane, and the feebly developed character of the opercular valves.
The alae have their upper margins oblique: they are only slightly, and sometimes not at all, added to above the level of the opercular membrane: their sutural edges are smooth.
If, however, the opercular membrane be rudely torn off before its proper period of exuviation, it carries with it the as yet continuous, but already modified, slip.
In a young specimen of this species, having the orifice of the shell only two tenths of an inch in diameter, I found the opercular membrane, as usual, double.
Of the older shells, which I examined and found living in the spring, nine tenths are now dead, the walls only remaining, the opercular valves having been washed away.
The aperture leading into the sack is bordered by very prominent lips, projecting above the opercular valves; the latter have their upper layers always scaled off.
The corium entering the parietal tubes, and lining the opercular valves, the mouth, and the anterior cirri, is generally of an extremely dark purple colour.
The opercular membrane is narrow; it is sometimes furnished with a few minute spines.
Apparently none of theopercular series was present.
The squamosal of Acanthostega (Jarvik, 1952) is articulated under the tabular and reaches forward and down, much as if it were an opercular in reversed position.
It is certainly the case that Spix published before Geoffroy the view that the opercular bones are homologous with the ear-ossicles, adopting, however, a different homology for the separate bones.
We may compare the similar thought that the ear ossicles are simply opercular bones reduced and turned to other uses.
He did not, however, himself realise the relation of the ear-ossicles to the gill-arches, though he knew that Spix and Geoffroy were quite wrong in homologising them with the opercularbones in fish.
The first memoir deals with the homologies of the opercular bones.
From the hinder edge of the hyoid arch grows out the membranous operculum, in which develop later the opercular bones and branchiostegal rays.
In addition to the bony elements belonging to the hyoid arch proper a series of membrane bones support the opercular flap.
The movements, however, of the four opercular valves are not at all more independent of the other valves, than in the other Pedunculated Cirripedes; and the peduncle is furnished with all its characteristic muscles.
In three days more, during which a new pair of branchial filaments had sprouted forth, the opercular peduncle had lost its lateral filaments (Figure 67), and the worms had become Serpulae.
Whence and for what purpose, if the Serpulae were produced or created as ready-formed species, these lateral filaments of the opercular peduncle?
The opercular apparatus is well developed, with numerous branchiostegals.
The family of swallowers Chiasmodontidæ, is made up of a few deep-sea fishes of soft flesh and feeble spines, the opercular apparatus much reduced.
The formidable opercular spines are weapons of defense, and when seized by the fisherman the fish is apt to throw its head in the direction of the hand and lance a spine into it.
Opercular bones all well developed, normal in position; the preopercle typically serrate.
The opercular apparatus is much reduced, and there are no branchiostegals.
They are therefore divested of both opercular and dorsal spines before being exposed for sale.
In Spirorbis Pagenstecheri they develop inside the opercular tentacle, and in Spirorbis spirillum inside the tube of the parent.
The embryo leaves its shell by the opercular aperture, and for some time swims rapidly about by means of its long cilia.
Operculum and opercular spine of the Lesser Weever 298 Fig.
The gland is an offshoot from the skin, and appears as a simple follicle invaginated in the opercular bone (fig.
In the Rascasse, the opercular spines of which are greatly developed, there is a rudiment of a poison-apparatus at the bottom of the sheath formed by the skin of the gills.
In this fish the præopercular bone ends in three strong, conical, and very sharp points, diverging like the prongs of a trident.
The spine surmounting the operculum exhibits a double cannelure connected with a conical cavity excavated in the thickness of the base of the opercular bone.
The upper margin of the opercular bone bears another point, which is directed upwards.
They have an elongate and but slightly compressed body, covered with ctenoid scales, and a large head in which the suborbital bones, which are broad, unite with the præopercular so as to form an osseous plate in the malar region.
Except in the case of the species of Muræna, the venom of fishes is generally found in one or more special glands, situate at the base of the dorsal or caudal fins, or beneath the opercular spines.
It is situated in the culs-de-sac formed by the opercular spines.
This is theopercular flap which covers the gills that lie beneath.
Bend the opercular flap backward over the eye and pin the entire fish, uncut side down, to the bottom of the dissecting-pan, covering it with water.
The opercular spine has a double channel in connection with a conical cavity hollowed out in the base of the opercular bone.
Behind the upper part of the pre-opercular is the largest of the opercular bones, the opercular proper.
The squamosal is probably homologous with the squamosal together with the pre-opercular of Bony Ganoids.
Its lower edge overlaps the sub-opercular, and both opercular and sub-opercular are overlapped by the infra-opercular (fig.
The infra-opercular is in its turn overlapped by the pre-opercular.
The opercular bones and those of the upper and lower jaws are quite comparable to those of bony Ganoids.
The last segment considered was the segment belonging to the VIIth nerve corresponding to the opercular appendages of the {291}Eurypterid.
The opercular segment is marked out by the thick black line.
In my specimens there is a distinct group of tubular muscles which pierce the opercular bar of muco-cartilage at its junction with the metastomal bar, and pass into the posterior group of velar muscles.
The above list will hopefully give you a few useful examples demonstrating the appropriate usage of "opercular" in a variety of sentences. We hope that you will now be able to make sentences using this word.
