Operculum sentence example

operculum
  • Above the mouth is the lid (operculum), which varies in size from a small narrow process to a large heartshaped expansion.
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  • Spire of shell much reduced; two bipectinate ctenidia, the right being the smaller; no operculum.
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  • Very usually, but not universally, the metapodium carries an operculum.
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  • Cyclostoma, shell turbinated, operculum calcareous, British.
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  • Foot divided into two, posterior half bearing the operculum; a wide epipodial velum; shell turbinated.
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  • Shell thin, more or less covered by the mantle; no operculum.
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  • Shell thin; operculum absent; tentacles bifid; foot secretes a float; pelagic. Janthina.
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  • Eulima, foot well developed, with an operculum, animal usually free, but some live in the digestive cavity of Holothurians.
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  • Visceral sac and shell coiled in one plane; foot divided transversely into two parts, posterior part bearing an operculum, anterior part forming a fin provided with a sucker.
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  • Visceral sac and shell small in proportion to the rest of the body, which cannot be withdrawn into the shell; foot elongated, fin-shaped, with sucker, but without operculum.
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  • Shell ovoid, with short spire and folded columella; foot small, no operculum; siphon short.
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  • A few Euthyneura in which the shell is not much reduced retain an operculum in the adult state, e.g.
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  • Cephalic disk enlarged anteriorly, forming an open tube posteriorly; shell external, thick, with p:ominent spire; no operculum.
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  • An operculum is present only in Amphibola; a contrast being thus afforded with the operculate pulmonate Streptoneura (Cyclostoma, &c.), which differ in other essential features of structure from the Pulmonata.
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  • Thus the whole of the Pulmonata (which breathe air, are destitute of gill-plumes and operculum and have a complicated hermaphrodite reproductive system) are either snails or slugs.
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  • The land-snails which have no gill-plume in the mantle-chamber and breathe air, but have the sexes separated, and possess an operculum, belong to the orders Aspidobranchia and Pectinibranchia, and constitute the families Helicinidae, Proserpinidae, Hydrocenidae, Cyclophoridae, Cyclostomatidae and Aciculidae.
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  • The first pair of foliaceous appendages in each animal is the genital operculum; beneath it are found the openings of the genital ducts.
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  • --Diagrams of the meta-sternite st, who showed that with genital operculum op, and the first lamellithe statements of gerous pair of appendages ga, with uniting von Graber were sternal element st of Scorpio (left) and Limulus erroneous, and (right).
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  • Whilst Limulus agrees thus closely with Scorpio in regard to the VII?tg VII, The genital operculum.
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  • The praegenital somite, VII PrG, is still present, but has lost its rudimentary appendages; go, the genital operculum, left half; Km, the left pecten; abp 4 to abp 7, the rudimentary appendages of the lung-sacs.
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  • The seventh, VII, is anterior to the genital operculum, op, and is the cavity of the praegenital somite which is more or less completely suppressed in subsequent development, possibly indicated by the area marked VII in fig.
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  • Mesosomatic segments furnished with large plate-like appendages, the 1st pair acting as the genital operculum, the remaining pairs being provided with branchial lamellae fitted for breathing oxygen dissolved in water.
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  • Though there are indications of lamelliform respiratory appendages on mesosomatic somites following that bearing the genital operculum, we cannot be said to have any proper knowledge as to such appendages, and further evidence with regard to them is much to be desired.
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  • The meeting of the coxae of all the prosomatic limbs in front of the pentagonal sternum; the space for a genital operculum; the pair of pectens, and the absence of any evidence of pulmonary stigmata are noticeable in this specimen.
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  • Genital orifice covered by an operculum.
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  • Genital orifice not covered by an operculum.
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  • Orifice closed, by a lid-like operculum.
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  • (iii.) In Umbonula of Cribrilina, showing the frontal membrane and parietal the entrance to the muscles of the young zooecium are like compensation - .sac on those of Membranipora, but they become the proximal side of the covered by the growth, from the proximal operculum (op).
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  • (vi.) In Microporella the opening of the compensation-sac has become separated from the operculum by calcareous matter, and is known as the "median pore."
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  • The operculum of the normal zooecium has become the mandible, while the occlusor muscles have become enormous.
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  • In its least differentiated form the avicularium occupies the place of an ordinary zooecium ("vicarious avicularium"), from which it is distinguished by the greater development of the operculum and its muscles, while the polypide is normally not functional.
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  • They occur in particular in relation with the orifice of the zooecium, and with that of the compensation-sac. This delicate structure is frequently guarded by an avicularium at its entrance, while avicularia are also commonly found on either side of the operculum or in other positions close to that structure.
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  • The foot is a muscular mass without cuticle or skeleton, excepting certain cuticular structures such as the byssus of Lamellibranchs and the operculum of Gastropods, which do not aid in locomotion.
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  • (In this Silurian genus the calyx is provided with a movable operculum, consisting of four paired triangular pieces, the bases of each being attached to the sides of the calyx, and their apices meeting in the middle when the operculum is closed).
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  • The simplest form to which they may be reduced is seen in the genital operculum of the scorpion.
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  • But Platylepas bissexlobata (De Blainville), from the west coast of Africa, is sometimes found entirely buried, except its operculum, in the skin of the manatee.
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  • The ventral and lateral parts of the anterior margin of the collar constitute the so-called operculum (op.), a structure which not only acts as a lower lip, but must be important in separating the food-current produced by the cilia of the tentacles from the external apertures of the collar-canals and gill-slits.
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  • Thus the arms are reduced to a single pair and possess no tentacles, there is no definite operculum, and the -alimentary canal is vestigial.
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  • Gena, foot elongated posteriorly, no operculum.
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  • ' Shell globular and ventricose; aperture oval and canaliculated; operculum spiral.
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  • Shell ventricose, with short spire, and wide aperture; no varices and no operculum; foot very broad, with projecting anterior angles; siphon long.
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  • Shell fusiform and solid, aperture elongated, columella folded; no operculum; eyes on sides of tentacles.
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  • Shell turriculated, with numerous whorls; aperture and operculum oval; eyes at summits of tentacles; siphon long.
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  • The shell of the Pulmonata, though always light and delicate, is in many cases a well-developed spiral " house," into which the creature can withdraw itself; and, although the foot possesses no operculum, yet in Helix the aperture of the shell is closed in the winter by a complete lid, the " hybernaculum," more or less calcareous in nature, which is secreted by the froot.
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  • 9, C) the compensationsac (c.s.) is a large cavity which lies beneath the calcified frontal wall and opens to the exterior at the proximal border of the operculum (fig.
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  • The Pulmonata have a straight visceral nerve-loop, usually no operculum even in the embryo, and a multidenticulate radula, the teeth being equi-formal; and they are hermaphrodite.
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  • If not preserved in an envelope the calyptra and operculum are very apt to fall off and become lost.
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  • The operculum retains its op..
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  • Shell spirally coiled; epipodial tentacles present; operculum thick and calcareous.
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