This results in a sinistrally coiled protoconch. The aperture is closed by an operculum.
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This results in a sinistrally coiled protoconch. The columella has one, spiral fold. The aperture is closed by an operculum.
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Both species described here are sinistrally coiled, but a similar pattern of ornamentation is present on two Pennsylvanian species that are dextrally coiled.
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Porcellioidea is an extinct superfamily of small to large sea snails, marine gastropod mollusks in the clade Vetigastropoda. This superfamily dates back to the Paleozoic. They developed sinistrally (left-handed) or planispirally coiled teleoconchs.
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The teleoconch is dextrally coiled, but the larval shells are sinistral. This results in a sinistrally coiled protoconch. The columella has usually one, but sometimes several, spiral folds. The aperture is closed by an operculum.
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Shells of Papillifera papillaris from the island of Malta. Scale bar is in mm. The shells of Papillifera papillaris are coiled sinistrally and, like other clausilids, extremely high-spired, with 10–11 whorls.M. P. Kerney.
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The adult shell, the teleoconch is dextrally coiled, but the larval shells are sinistral. This results in a sinistrally coiled protoconch. The opening of the shell, the aperture is closed by a lid, a so called operculum.
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Lorieroceras lorieri is an extinct oncocerid nautilitoidean cephalopod belonging to the family Nothoceratidae. Fossils are found in Lower Devonian marine strata of France. Its shell is unusual among nautiloids in that it is a loosely coiled, turban-shaped helix that is sinistrally coiled.
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The shells of Limacina are well developed, sinistrally coiled, turret-like, and include an operculum. Shell size and thickness vary within the genus. At high latitudes, the diameter of the shell does not exceed 15 mm. At lower latitudes, the diameter varies from 1 to 3 mm.
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There is little known about their life histories. Most species are only known from their shells. Most species have a white of yellowish, minute, conical to ovate-conical shell, usually between 2 mm and 5 mm. The apex is rather obtuse or nipple-shaped, sinistrally or dextrally oriented to the teloconch.
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Snails of this family are spiralled sinistrally, with the opening hole slanted downward toward the right. Large folds of skin may protrude out of the more open left side. Like all air-breathing water snails, the animal has no operculum, and has only one pair of tentacles with the eye spots at the base of the tentacles. Ramshorn snails have a lifespan on one year .
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Species in the genus Amphidromus usually have smooth, glossy, brightly colored, elongate or conic, dextrally or sinistrally coiled shells. The shells are moderately large, ranging from to in maximum dimension, having from 6 to 8 convex whorls. Their color pattern is usually monochromatic yellowish or greenish, but can be variegated. The aperture is oblique or ovate in shape, without any teeth or folds, and with the aperture height ranging from two-fifths to one-third of total shell height.
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A trough, approximately deep, borders the north along this transform boundary to the east connecting to a deep hole, called the "Pito Deep" because of its close proximity to the Pito Seamount, at the northeastern limit. The western border is divided into two parts. The west section has 2 spreading segments running north to south with spreading rates that approximately range from /yr. These segments are connected by sinistrally slipping transform faults around 14°15' S. A relay basin runs north to south along the southernmost segment as a result of past counter-clockwise rotation.
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The earliest genus included in the Nephriticeraatidae is the sinistrally torticconic Sphyradoceras, which comes from the Lower Devonian Schoharie Formation of New York. It is in fact the only torticonic genus in the family and the only genus known from the Barrandeocerina from the Lower Devonian. The early stage of Sphyradoceras is gyroconic, coiled in a plane but with whorls not touching, resembling the adult stage of the barrandeoceratid genus Bickmorites. This might suggest that the Nephriticeratidae has its origin in the Barrandeoceratidae, from Bickmorites, however the latest Bickmorites are from the Middle Silurian, leaving a gap in the Upper Silurian with no intermediary forms.
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