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Hemisurcula
''Hemisurcula'' is an extinct genus of sea snails, marine gastropod mollusks in the family Clavatulidae.Marshall, B. (2015). Hemisurcula Casey, 1904 †. In: MolluscaBase (2015). Accessed through: World Register of Marine Species at http://www.marinespecies.org/aphia.php?p=taxdetails&id=829411 on 2016-06-11 Description (Original description) In this genus the shell is fusiform, with the protoconch conoidal, multispiral and closely coiled. The nepionic (= relating to the stage of development succeeding the embryonic) spire whorls alone are costate and have also an elevated collar below the suture. The more recent whorls become devoid of lyrae or costae, though having throughout densely close-set and subequal microscopic striae, except the body whorl abruptly below the posterior end of the aperture, which is obliquely and rather coarsely lyrate. The siphonal canal is moderate, straight, and, together with the aperture, forms about half the length of the shell. The sinus is broad ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hemisurcula Terus
''Hemisurcula'' is an extinct genus of sea snails, marine gastropod mollusks in the family Clavatulidae.Marshall, B. (2015). Hemisurcula Casey, 1904 †. In: MolluscaBase (2015). Accessed through: World Register of Marine Species at http://www.marinespecies.org/aphia.php?p=taxdetails&id=829411 on 2016-06-11 Description (Original description) In this genus the shell is fusiform, with the protoconch conoidal, multispiral and closely coiled. The nepionic (= relating to the stage of development succeeding the embryonic) spire whorls alone are costate and have also an elevated collar below the suture. The more recent whorls become devoid of lyrae or costae, though having throughout densely close-set and subequal microscopic striae, except the body whorl abruptly below the posterior end of the aperture, which is obliquely and rather coarsely lyrate. The siphonal canal is moderate, straight, and, together with the aperture, forms about half the length of the shell. The sinus is broadly r ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Clavatulidae
Clavatulidae is a taxonomic family of sea snails, marine gastropod mollusks in the superfamily Conoidea. The family is not well differentiated morphologically. Clavatulidae was raised, based on cladistic analysis, from subfamily to the family level by Rosenberg in 1998. It is no longer regarded as a subfamily of Turridae by several malacologists (Kantor, Sysoev).World Register of Marine Species: Clavatulidae accessed 1 April 2010. This family has no subfamilies. General characteristics This family consists of species with a medium-sized to rather large, fusiform shell. The oblong, pointed spire is rather high. The[...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Eocene
The Eocene ( ) Epoch is a geological epoch that lasted from about 56 to 33.9 million years ago (mya). It is the second epoch of the Paleogene Period in the modern Cenozoic Era. The name ''Eocene'' comes from the Ancient Greek (''ēṓs'', " dawn") and (''kainós'', "new") and refers to the "dawn" of modern ('new') fauna that appeared during the epoch. The Eocene spans the time from the end of the Paleocene Epoch to the beginning of the Oligocene Epoch. The start of the Eocene is marked by a brief period in which the concentration of the carbon isotope 13C in the atmosphere was exceptionally low in comparison with the more common isotope 12C. The end is set at a major extinction event called the ''Grande Coupure'' (the "Great Break" in continuity) or the Eocene–Oligocene extinction event, which may be related to the impact of one or more large bolides in Siberia and in what is now Chesapeake Bay. As with other geologic periods, the strata that define the start and e ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Protoconch
A protoconch (meaning first or earliest or original shell) is an embryonic or larval shell which occurs in some classes of molluscs, e.g., the initial chamber of an ammonite or the larval shell of a gastropod. In older texts it is also called "nucleus". The protoconch may sometimes consist of several whorls, but when this is the case, the whorls show no growth lines. The whorls of the adult shell, which are formed after the protoconch, are known as the teleoconch. The teleoconch starts forming when the larval gastropod becomes a juvenile, and the protoconch may dissolve. Quite often there is a visible line of demarcation where the protoconch ends and the teleoconch begins, and there may be a noticeable change in sculpture, or a sudden appearance of sculpture at that point. In some gastropod groups (such as the Architectonicidae), the teleoconch whorls spiral in the opposite direction to the protoconch. In those cases, the shell is called heterostrophic. In species whic ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Whorl (mollusc)
A whorl is a single, complete 360° revolution or turn in the spiral growth of a mollusc shell. A spiral configuration of the shell is found in numerous gastropods, but it is also found in shelled cephalopods including '' Nautilus'', '' Spirula'' and the large extinct subclass of cephalopods known as the ammonites. A spiral shell can be visualized as consisting of a long conical tube, the growth of which is coiled into an overall helical or planispiral shape, for reasons of both strength and compactness. The number of whorls which exist in an adult shell of a particular species depends on mathematical factors in the geometric growth, as described in D'Arcy Wentworth Thompson's classic 1917 book '' On Growth and Form'', and by David Raup. The main factor is how rapidly the conical tube expands (or flares-out) over time. When the rate of expansion is low, such that each subsequent whorl is not that much wider than the previous one, then the adult shell has numerous whorl ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Alabama
(We dare defend our rights) , anthem = " Alabama" , image_map = Alabama in United States.svg , seat = Montgomery , LargestCity = Huntsville , LargestCounty = Baldwin County , LargestMetro = Greater Birmingham , area_total_km2 = 135,765 , area_total_sq_mi = 52,419 , area_land_km2 = 131,426 , area_land_sq_mi = 50,744 , area_water_km2 = 4,338 , area_water_sq_mi = 1,675 , area_water_percent = 3.2 , area_rank = 30th , length_km = 531 , length_mi = 330 , width_km = 305 , width_mi = 190 , Latitude = 30°11' N to 35° N , Longitude = 84°53' W to 88°28' W , elevation_m = 150 , elevation_ft = 500 , elevation_max_m = 735.5 , elevation_max_ft = 2,413 , elevation_max_point = Mount Cheaha , elevation_min_m = 0 , elevation_min_ft = 0 , elevation_min_point = Gulf of Mexico , OfficialLang = English , Languages = * English 95.1% * Spanish 3.1% , population_demonyms = Alabamian (We dare defend our rights) , anthem = "Alabama (state song), Alabama" , i ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Genus
Genus ( plural genera ) is a taxonomic rank used in the biological classification of living and fossil organisms as well as viruses. In the hierarchy of biological classification, genus comes above species and below family. In binomial nomenclature, the genus name forms the first part of the binomial species name for each species within the genus. :E.g. '' Panthera leo'' (lion) and '' Panthera onca'' (jaguar) are two species within the genus ''Panthera''. ''Panthera'' is a genus within the family Felidae. The composition of a genus is determined by taxonomists. The standards for genus classification are not strictly codified, so different authorities often produce different classifications for genera. There are some general practices used, however, including the idea that a newly defined genus should fulfill these three criteria to be descriptively useful: # monophyly – all descendants of an ancestral taxon are grouped together (i.e. phylogenetic analysis should c ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Columella (gastropod)
The columella (meaning "little column") or (in older texts) pillar is a central anatomical feature of a coiled snail shell, a gastropod shell. The columella is often only clearly visible as a structure when the shell is broken, sliced in half vertically, or viewed as an X-ray image. The columella runs from the apex of the shell to the midpoint of the undersurface of the shell, or the tip of the siphonal canal in those shells which have a siphonal canal. If a snail shell is visualized as a cone of shelly material which is wrapped around a central axis, then the columella more or less coincides spatially with the central axis of the shell. In the case of shells that have an umbilicus, the columella is a hollow structure. The columella of some groups of gastropod shells can have a number of plications or folds (the columellar fold, plaits or plicae), which are usually visible when looking to the inner lip into the aperture of the shell. These folds can be wide or narrow, promine ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sea Snail
Sea snail is a common name for slow-moving marine gastropod molluscs, usually with visible external shells, such as whelk or abalone. They share the taxonomic class Gastropoda with slugs, which are distinguished from snails primarily by the absence of a visible shell. Definition Determining whether some gastropods should be called sea snails is not always easy. Some species that live in brackish water (such as certain neritids) can be listed as either freshwater snails or marine snails, and some species that live at or just above the high tide level (for example species in the genus '' Truncatella'') are sometimes considered to be sea snails and sometimes listed as land snails A land snail is any of the numerous species of snail that live on land, as opposed to the sea snails and freshwater snails. ''Land snail'' is the common name for terrestrial gastropod mollusks that have shells (those without shells are known .... Anatomy Sea snails are a very large group o ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Aperture (mollusc)
The aperture is an opening in certain kinds of mollusc shells: it is the main opening of the shell, where the head-foot part of the body of the animal emerges for locomotion, feeding, etc. The term ''aperture'' is used for the main opening in gastropod shells, scaphopod shells, and also for '' Nautilus'' and ammonite shells. The word is not used to describe bivalve shells, where a natural opening between the two shell valves in the closed position is usually called a '' gape''. Scaphopod shells are tubular, and thus they have two openings: a main anterior aperture and a smaller posterior aperture. As well as the aperture, some gastropod shells have additional openings in their shells for respiration; this is the case in some Fissurellidae (keyhole limpets) where the central smaller opening at the apex of the shell is called an orifice, and in the Haliotidae (abalones) where the row of respiratory openings in the shell are also called orifices. In gastropods In some pros ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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