proboscidean: …sirenians are together classified as tethytherians, in reference to the ancient sea of Tethys, where both groups are hypothesized to have originated. On land the closest proboscidean relative is the hyrax (order Hyracoidea), a small rodentlike animal of Africa and southwestern Asia. Tethytheria and Hyracoidea are grouped together as Uranotheria.

ancient Egypt: The 6th dynasty (c. 2305–c. 2118 bce): …the reigns of Unas and Teti, the first king of the 6th dynasty. Around Teti’s pyramid in the northern portion of Ṣaqqārah was built a cemetery of large tombs, including those of several viziers. Together with tombs near the pyramid of Unas, this is the latest group of private monuments…

Îles du Vent: Tetiaroa, 25 miles (40 km) north of Tahiti, comprises 13 islets, with a total area of 2.5 square miles (6.5 square km). Mehetia (1 square mile [2.6 square km]), 60 miles (95 km) east of Tahiti, is uninhabited.

Glen Tetley was an American dancer, choreographer, and ballet director, whose performances and compositions integrated elements of modern dance and classical ballet. Tetley began his dance career relatively late for a professional performer. In 1946, dissatisfied with his premedical studies at

Glen Tetley was an American dancer, choreographer, and ballet director, whose performances and compositions integrated elements of modern dance and classical ballet. Tetley began his dance career relatively late for a professional performer. In 1946, dissatisfied with his premedical studies at

Kazimierz Tetmajer was a poet and short-story writer who was a member of the Young Poland movement. Tetmajer belonged to a landowner’s family from the foothills of the Tatra Mountains. He studied philosophy in Kraków and in Heidelberg, Germany. Much of his lyric poetry received publication in the

Kazimierz Tetmajer was a poet and short-story writer who was a member of the Young Poland movement. Tetmajer belonged to a landowner’s family from the foothills of the Tatra Mountains. He studied philosophy in Kraków and in Heidelberg, Germany. Much of his lyric poetry received publication in the

Georgia: Relief, drainage, and soils: …in Georgia, and Mounts Rustaveli, Tetnuld, and Ushba, all of which are above 15,000 feet. The cone of the extinct Mkinvari (Kazbek) volcano dominates the northernmost Bokovoy range from a height of 16,512 feet. A number of important spurs extend in a southward direction from the central range, including those…

Black Hills: …and sacred territory of the Western Sioux Indians. At least portions of the region were also sacred to other Native American peoples—including the Cheyenne, Kiowa, and Arapaho—and the area had also been inhabited by the Crow. Rights to the region were guaranteed to Sioux and Arapaho by the Second Treaty…

Snake River: In 1976 the Teton Dam collapsed, causing disastrous flooding of the upper Snake River valley. Principal tributaries below Heise are Henrys Fork (the largest), Blackfoot, Portneuf, Raft, and Big Wood rivers. Henrys Fork and Big Wood enter the Snake River from the north. Other northern side streams sink…

Teton Range, segment of the Middle Rocky Mountains in the western United States, extending southward for 40 miles (64 km) across northwestern Wyoming, from the southern boundary of Yellowstone National Park to Teton Pass, just west of Jackson. Some foothills reach into southeastern Idaho. Many

Teton River, river in Teton county, north-central Montana, U.S. The Teton rises northeast of the Sun River on the east slopes of the Continental Divide and is joined from the south by Deep Creek and from the north by Muddy Creek. It flows 143 miles (230 km) east and slightly south, joining the

Tétouan, city, north-central Morocco. It lies along the Martil River (Wadi Martil), 7 miles (11 km) from the Mediterranean Sea. The city stands on a rocky plateau detached from the southern flank of Mount Dersa. The Roman settlement of Tamuda stood immediately above the present-day city. Tétouan

tetra, any of numerous attractively coloured freshwater fishes of the characin family, Characidae, often kept in home aquariums. Tetras are characteristically small, lively, hardy, and unaggressive. They are native to South America and Africa. Tetras are egg layers and breed, as do most other

cement: Chemical composition: … (3CaO · Al2O3), and a tetra-calcium aluminoferrite (4CaO · Al2O3Fe2O3). In an abbreviated notation differing from the normal atomic symbols, these compounds are designated as C3S, C2S, C3A, and C4AF, where C stands for calcium oxide (lime), S for silica, A for alumina, and F for iron

Ptolemy: Astronomer: …Influences”), later known as the Tetrabiblos for its four volumes. He believed that astrology is a legitimate, though inexact, science that describes the physical effects of the heavens on terrestrial life. Ptolemy accepted the basic validity of the traditional astrological doctrines, but he revised the details to reconcile the practice…

cephalopod: Critical appraisal: …forms, which were considered as Tetrabranchia because Nautilus has four gills rather than two. This unnatural classification, accepted by the French zoologist Alcide d’Orbigny in 1838, was gradually modified through the efforts of the Swiss zoologist Adolph Naef and the German zoologist Georg Grimpe and later workers to the form…

microplastics: Properties: …polybrominated diphenyl ethers (PBDEs), and tetrabromobisphenol A (TBBPA), are typically also present in microplastics, and many of these chemical additives leach out of the plastics after entering the environment.

bromine: Production and use: …various dyes and the compounds tetrabromoethane (C2H2Br4) and bromoform (CHBr3), which are used as liquids in gauges because of their high specific gravity. Until the development of barbiturates in the early 20th century, bromides of potassium, sodium, calcium, strontium

dye: Xanthene and related dyes: Tetrabromofluorescein, or eosin, is a red dye used for paper, inks, and cosmetics; its tetraiodo analog, erythrosine, is a red food dye (see below Food dyes).

nickel: Compounds: …other important commercial compounds are nickel carbonyl, or tetracarbonylnickel, Ni(CO)4. This compound, in which nickel exhibits a zero oxidation state, is used primarily as a carrier of carbon monoxide in the synthesis of acrylates (compounds utilized in the manufacture of plastics) from acetylene and alcohols. It was the first of…

magnoliid clade: Vegetative structures: The exceptions, Trochodendron (Trochodendraceae) and Tetracentron (Tetracentraceae), show definite links with the magnoliids but are classified in the Eudicot clade. Of the magnoliids, all Winteraceae (Canellales) and Amborellaceae (Laurales) lack vessels.

Trochodendrales: Tetracentron sinense, of central and south-central China, Nepal, and northern Myanmar (Burma), is a medium-sized tree, 4.5 to 27 metres (about 15 to 88.5 feet) tall, with palmately (fingerlike) veined leaves. Unlike Trochodendron, Tetracentron has small, wind-pollinated flowers arranged in dangling, slender catkins; the flowers…

tetrachloroethylene, a colourless, dense, nonflammable, highly stable liquid belonging to the family of organic halogen compounds. Tetrachloroethylene is a powerful solvent for many organic substances. By the mid-20th century it had become the most widely used solvent in dry cleaning (displacing

tetrachloroethane, either of two isomeric colourless, dense, water-insoluble liquids belonging to the family of organic halogen compounds. One isomer, 1,1,2,2-tetrachloroethane, also called acetylene tetrachloride, is highly toxic. Almost the entire production of the compound is consumed in

tetrachloroethylene, a colourless, dense, nonflammable, highly stable liquid belonging to the family of organic halogen compounds. Tetrachloroethylene is a powerful solvent for many organic substances. By the mid-20th century it had become the most widely used solvent in dry cleaning (displacing

carbon tetrachloride, a colourless, dense, highly toxic, volatile, nonflammable liquid possessing a characteristic odour and belonging to the family of organic halogen compounds, used principally in the manufacture of dichlorodifluoromethane (a refrigerant and propellant). First prepared in 1839 by

chlorophenol: Tetrachlorophenol is an insecticide and a bactericide and is used as a preservative for latex, wood, and leather. Pentachlorophenol (PCP) is a disinfectant, a fungicide, and an extremely effective preservative for wood. However, the U.S. Environmental Protection Agency has regulations requiring that it be applied…

tetrachord, musical scale of four notes, bounded by the interval of a perfect fourth (an interval the size of two and one-half steps, e.g., c–f). In ancient Greek music the descending tetrachord was the basic unit of analysis, and scale systems (called the Greater Perfect System and the Lesser

arartree, (Tetraclinis articulata), only species of the genus Tetraclinis of the cypress family (Cupressaceae), found in hot, dry areas of southeastern Spain, Malta, and northern Africa. A pyramidal tree 12 to 15 metres (about 40 to 50 feet) tall, the arartree has fragrant, brown or reddish-brown

tetracolon, in classical prosody, a period made up of four colons, or a unit of four metrical sequences that each constitute a single metrical phrase of not more than about 12 syllables. A tetracolon recurs as a unit within a

Tetractinella, genus of extinct brachiopods (lamp shells) found as fossils in Triassic marine rocks (the Triassic period lasted from 251 million to 200 million years ago). Its distinctive shell has prominent ribs and intervening troughs radiating from its apex and margins extending in a weblike

Tetractinella: Tetractinella trigonella, a Middle Triassic species from Italy, is remarkably similar to the unrelated Cheirothyris fleuriausa, from the Late Jurassic (about 150 million years ago) marine rocks of Germany. The two forms are separated by a great geographic distance and by a large span of…

tetracycline, any of a group of broad-spectrum antibiotic compounds that have a common basic structure and are either isolated directly from several species of Streptomyces bacteria or produced semisynthetically from those isolated compounds. Tetracyclines act by interfering with the ability of a

meiosis: Each pair of chromosomes—called a tetrad, or a bivalent—consists of four chromatids. At this point, the homologous chromosomes exchange genetic material by the process of crossing over (see linkage group). The homologous pairs line up along the midline of the cell in metaphase I and then separate in anaphase I,…

coccus: …cells in a square arrangement, tetrads. These characteristic groupings occur as a result of variations in the reproduction process in bacteria. See also Staphylococcus; Streptococcus.

carboxylic acid: Saturated aliphatic acids: …from C12 to C18 (lauric, myristic, palmitic, and stearic), are present in the fats and oils of many animals and plants, with palmitic and stearic acids being the most prevalent. Lauric acid (C12) is the main acid in coconut oil (45–50 percent) and palm kernel oil (45–55 percent). Nutmeg butter…

tetradymite, a sulfide mineral of bismuth and tellurium (Bi2Te2S). It is commonly found in gold-quartz veins and contact-metamorphic deposits, as in Idu, Japan; Sorata, Bolivia; Boliden, Sweden; and Boulder county, Colo., U.S. Tetradymite is classified in a group of metallike sulfide minerals

tetraethyl lead (TEL), organometallic compound containing the toxic metal lead that for much of the 20th century was the chief antiknock agent for automotive gasoline, or petrol. Beginning in the 1970s, “leaded gasoline” was phased out, first in the United States and then in Europe and around the

tetraethyl pyrophosphate, an organic phosphorus compound used as an insecticide, particularly for the control of aphids and red spider mites. Tetraethyl pyrophosphate is extremely poisonous to humans, the toxic effects being similar to those of parathion. It decomposes in water to nontoxic esters

drug: Drugs that affect skeletal muscle: …that facilitate acetylcholine release, including tetraethylammonium and 4-aminopyridine. They work by blocking potassium-selective channels in the nerve membrane, thereby prolonging the electrical impulse in the nerve terminal and increasing the amount of acetylcholine released. This can effectively restore transmission under certain conditions, but these drugs are not selective enough for…

tetraethyl lead (TEL), organometallic compound containing the toxic metal lead that for much of the 20th century was the chief antiknock agent for automotive gasoline, or petrol. Beginning in the 1970s, “leaded gasoline” was phased out, first in the United States and then in Europe and around the

organosulfur compound: Thiocarbonyl compounds: The related compound disulfiram (Antabuse; R = CH2CH3) is used in treating alcoholism. A thioamide, ethionamide, is an important drug used in the treatment of tuberculosis, and other thioamides are used as peptide analogs and in peptide synthesis.

tetrafluoroethylene, a colourless, odourless, faintly toxic gas belonging to the family of organic halogen compounds; it is the starting material in the manufacture of polytetrafluoroethylene (q.v.), a valuable synthetic resin. Tetrafluoroethylene is produced by heating chlorodifluoromethane, which

chimera: The different tissues of tetragametic chimeras are made up of cells derived from one or both zygotes; for example, while one tissue type may consist of cells from one zygote, other tissues may consist of cells from the other zygote or may be cellular composites of both zygotes. Indications…

chimera: … fuse together, producing a so-called tetragametic individual—an individual originating from four gametes, or sex cells. (Under normal circumstances, in the absence of zygote fusion, two fertilized eggs result in the production of dizygotic, or fraternal, twins.) Dispermic chimerism can also occur when a zygote fuses with a fertilized polar body…

spider: Annotated classification: Family Tetragnathidae (long-jawed orb weavers) 1,000 species worldwide. Males with long chelicerae; epigynum often secondarily lost. Family Pholcidae (daddy longlegs spiders) About 960 species worldwide. Similar to the nonspiders called daddy longlegs of the order Opiliones.

tetragonal system, one of the structural categories to which crystalline solids can be assigned. Crystals in this system are referred to three mutually perpendicular axes, two of which are equal in length. If the atoms or atom groups in the solid are represented by points and the points are

perciform: Annotated classification: Ariommidae, Amarsipidae, and Tetragonuridae Eocene to present; slender to ovate, deep-bodied fishes; dorsal fin continuous or spinous portion set off from soft portion by deep notch; in the most generalized species, which resemble Kyphosidae, the soft dorsal is preceded by about 6 low, stoutish spines; other species resemble…

Yahweh, name for the God of the Israelites, representing the biblical pronunciation of “YHWH,” the Hebrew name revealed to Moses in the book of Exodus. The name YHWH, consisting of the sequence of consonants Yod, Heh, Waw, and Heh, is known as the tetragrammaton. After the Babylonian Exile (6th

pentagram: …this concept with the “tetragrammaton pentagram,” which includes a variety of symbols that represent human existence. In addition to planetary and astrological symbols, this pentagram includes symbols of the four elements and Hebrew letters. The pentagram was also used by the Freemasons, who sometimes placed a G in the…

Tetragraptus, genus of extinct graptolites (colonial animals related to the chordates) that occur as fossils in marine rocks of the Early Ordovician Epoch (505 to 478 million years ago). The genus is a useful guide, or index, fossil for the Early Ordovician; long-distance correlations between rock

chemical bonding: Molecular shapes and VSEPR theory: …one another, as in the tetrahedral arrangement of hydrogen atoms around the central carbon atom in methane, CH4, or the angular arrangement of atoms in H2O.

continent: …as explanation are: (1) the tetrahedral (four-faced) theory, in which a cooling earth assumes the shape of a tetrahedron by spherical collapse; (2) the accretion theory, in which younger rocks attached to older shield areas became buckled to form the landforms; (3) the continental-drift theory, in which an ancient floating…

amphibole: Crystal structure: …(t-o-t) strips, also known as I beams, are approximately twice as wide in the b direction as the equivalent t-o-t strips in pyroxenes because of the doubling of the chains in the amphiboles. The t-o-t I beams are schematically shown in Figure 4B. The structure ruptures around the stronger I…

tetrahedrite, common sulfosalt mineral, an antimony sulfide of copper, iron, zinc, and silver [(Cu,Fe,Zn,Ag)12Sb4S13], that is an important ore of copper and sometimes of silver. It forms gray to black metallic crystals or masses in metalliferous hydrothermal veins. Tetrahedrite forms a solid

clay mineral: General features: These features are continuous two-dimensional tetrahedral sheets of composition Si2O5, with SiO4 tetrahedrons (Figure 1) linked by the sharing of three corners of each tetrahedron to form a hexagonal mesh pattern (Figure 2A). Frequently, silicon atoms of the tetrahedrons are partially substituted for by aluminum and, to a lesser extent,…

tetrahydrocannabinol (THC), active constituent of marijuana and hashish that was first isolated from the Indian hemp plant (Cannabis sativa) and synthesized in 1965. For the effects of the drug, see

ether: Complexes of ethers with reagents: …as its liquid complex with tetrahydrofuran (THF). Similarly, gaseous boron trifluoride (BF3) is more easily used as its liquid complex with diethyl ether, called BF3 etherate, rather than as the toxic, corrosive gas.

pyran: …members of this family is tetrahydropyran, made by hydrogenating the dihydro compound. Sugars often occur in pyranose forms containing the tetrahydropyran ring: a typical example is the glucose unit present in sucrose, starch, cellulose, and glycogen.

hymenostome: …the even more widely studied genus Tetrahymena, which can be easily cultured for biochemical and physiological research. The hymenostomes are characterized by a ventral mouth cavity, which is lined by three membranelles of fused cilia on one side and by an undulating membrane on the other side. In the genus…

thyroxine, one of the two major hormones secreted by the thyroid gland (the other is triiodothyronine). Thyroxine’s principal function is to stimulate the consumption of oxygen and thus the metabolism of all cells and tissues in the body. Thyroxine is formed by the molecular addition of iodine to

organosulfur compound: Sulfuranes: hypervalent organosulfur compounds: …example, the σ-sulfurane (C6F5)4S, named tetrakis-(pentafluorophenyl)sulfurane, prepared at temperatures below 0 °C (32 °F), decomposes to C6F5C6F5 and C6F5SC6F5 upon warming. On the other hand, if protected from moisture, acyclic and cyclic dialkyloxysulfuranes of type R2(R′O)2S are stable at room temperature and find utility as reagents in organic synthesis.

Pythagoreanism: General features of Pythagoreanism: …sometimes mystical, such as the tetraktys, the golden section, and the harmony of the spheres; (5) the Pythagorean theorem; and (6) the demand that members of the order shall observe a strict loyalty and secrecy.

Tetramelaceae, small family of the squash order (Cucurbitales) of flowering plants containing two genera, each with one species. Octomeles sumatrana is among the tallest trees in the forests of Malesia. Tetrameles nudiflora, a tree that grows from Central and East Asia to Australia, has male and

Cucurbitales: Other families: Tetramelaceae includes two genera (Tetrameles and Octomeles) of Indo-Malesian (see Malesian subkingdom) trees, each with one species. Male and female flowers occur on different trees and are borne in pendulous spikes. The ovary is inferior, with the ovules borne on the walls, and the short styles are borne in…

Tetramelaceae: Tetrameles nudiflora, a tree that grows from Central and East Asia to Australia, has male and female blooms on separate trees. The flowers are small and the fruits are dry, splitting open to release the tiny seeds.

evolution: Molecular phylogeny of genes: Hemoglobin molecules are tetramers (molecules made of four subunits), consisting of two polypeptides (relatively short protein chains) of one kind and two of another kind. In embryonic hemoglobin E, one of the two kinds of polypeptide is designated ε; in fetal hemoglogin F, it is γ; in adult…

Tetrameristaceae: The three species of Tetramerista grow in Southeast Asia, and the single species of Pentamerista grows in the Guiana Highlands of Venezuela. Both genera have spiral short-stalked leaves with indistinct venation and marginal glands and bear fleshy fruits that are presumably dispersed by animals. Tetramerista has glistening dots on…

Tetrameristaceae, flowering plant family of the order Ericales, composed of three genera of woody trees and small shrubs. Members of the family are characterized by flowers with glands on the inner surfaces of the sepals, five stamens, and only a single ovule in each part of the ovary. The genus

tetrameter, line of poetic verse that consists of four metrical feet. In English versification, the feet are usually iambs (an unstressed syllable followed by a stressed one, as in the word ˘be|cause´ ), trochees (a stressed syllable followed by an unstressed one, as in the word ti´|ger),˘ or a

arsenic: Commercial production and uses: …organic compounds, as for example tetramethyl diarsine, (CH3)2As―As(CH3)2, used in preparing the common desiccant cacodylic acid. Several complex organic compounds of arsenic have been employed in the treatment of certain diseases, such as amebic dysentery, caused by microorganisms.

organosulfur compound: Occurrence and preparation: The solvent sulfolane (thiolane S,S-dioxide) is prepared by first reacting sulfur dioxide with butadiene to give sulfolene (a cyclic, unsaturated, five-membered ring sulfone), followed by hydrogenation to yield sulfolane.

chemical compound: Proton magnetic resonance spectroscopy: …the protons in the compound tetramethylsilane, (CH3)4Si. Tetramethylsilane is an inert liquid added in small amounts to the compound being analyzed. All 12 of its hydrogen atoms absorb at the same position to give a single sharp peak, which is arbitrarily assigned a positional value of zero. This peak is…

red spider, any of the plant-feeding mites of the family Tetranychidae (subclass Acari). Red spiders are a common pest on houseplants and agriculturally important plants, including the foliage and fruit of orchard trees. The life cycle of the red spider from egg to adult takes about three weeks.

grouse: …Old World member is the black grouse (Lyrurus tetrix), of Wales, Scotland, Scandinavia, and north-central Europe; a related form (L. mlokosiewiczi) occurs in the Caucasus. The male, known as blackcock, may be 55 cm (22 inches) long and weigh almost 2 kg (about 4 pounds). He is iridescent blue-black, with…

capercaillie, European game bird of the grouse family. See

puffer, any of about 90 species of fishes of the family Tetraodontidae, noted for their ability when disturbed to inflate themselves so greatly with air or water that they become globular in form. Puffers are found in warm and temperate regions around the world, primarily in the sea but also, in

tetraodontiform, (order Tetradontiformes), any member of a group of primarily tropical marine fishes that are closely related to the perciforms (the typical advanced spiny-rayed fishes) that evolved during the Eocene Period of the Cenozoic Era, about 50 million years ago. Included are the

tetraodontiform, (order Tetradontiformes), any member of a group of primarily tropical marine fishes that are closely related to the perciforms (the typical advanced spiny-rayed fishes) that evolved during the Eocene Period of the Cenozoic Era, about 50 million years ago. Included are the

tetraodontiform: Annotated classification: Suborder Tetraodontoidei (Gymnodontes) 4 tooth plates, 2 in each jaw; skin bearing small erectile spines. Family Triodontidae (threetooth puffers) Most primitive member of the superfamily, the only species to retain even the pelvic bone of the pelvic fin apparatus (completely lost by all other members of…

fish poisoning: Tetraodon poisoning is caused by the ingestion of certain species of pufferlike fish found in Far Eastern waters. These fishes contain a potent, heat-stable toxin that affects the human nervous system, producing symptoms within minutes. Dizziness and tingling about the lips and tongue may soon…

grouse, any of a number of game birds in the family Tetraonidae (order Galliformes). In addition to species called grouse, the group includes several birds known by particular names, such as the capercaillie and prairie chicken (see below) and the ptarmigan. The order Columbiformes contains the

rice-paper plant, (species Tetrapanax papyriferum), shrub or small tree of the ginseng family (Araliaceae), native to southern China and Taiwan. It is the source of rice paper. It has large, lobed leaves that form an almost palmlike crown. The central tissues of the stem are split and pressed into

Epicureanism: Doctrine of Epicurus: …all his wisdom is the Tetrapharmacon, preserved by Philodemus: “The gods are not to be feared. Death is not a thing that one must fear. Good is easy to obtain. Evil is easy to tolerate.”

bryophyte: Annotated classification: Subclass Tetraphidae Sporophytes with elongate seta; sporangium opening by an operculum exposing four multicellular peristome teeth that respond to moisture change to release spores gradually; spore layer forming a cylinder around central columella; protonema filamentous but with thallose flaps; gametophores erect, with rhizoids at base, leaves…

bryophyte: Annotated classification: …Hemisphere; 1 order, 2 genera, Tetraphis and Tetrodontium, with 3 or 5 species. The family Calomniaceae (1 genus, with about 9 species) is sometimes included in this subclass. Subclass Polytrichidae Sporophytes with elongate rigid seta containing conducting system; sporangium opening by operculum; numerous multicellular peristome teeth in a single concentric…

nitrile: …formed by heating amides with phosphorous pentoxide. They can be reduced to primary amines through the action of lithium aluminum hydride or hydrolyzed to carboxylic acids in the presence of either an acid or a base.

oxide: Oxides of phosphorus: …common oxides, phosphorus(III) oxide (or tetraphosphorus hexoxide), P4O6, and phosphorus(V) oxide (or tetraphosphorus decaoxide), P4O10. Both oxides have a structure based on the tetrahedral structure of elemental white phosphorus. Phosphorus(III) oxide is a white crystalline solid that smells like garlic and has a poisonous vapour. It oxidizes slowly in air…

flatworm: Annotated classification: Order Tetraphyllidea Scolex with 4 bothridia (leaflike muscular structure); vitellaria located in lateral margins of proglottids; genital pores lateral; parasites of elasmobranchs; about 200 species. Order Lecanicephalidea Reproductive system similar to Tetraphyllidea, but scolex divided into an upper disklike or globular part and a lower collarlike…

Poaceae: Economic and ecological importance: …diploid (2n), the normal condition; tetraploid (2n = 14, resulting from the fusion of diploid gametes); and hexaploid (2n = 21). An example of a domesticated diploid wheat is einkorn wheat (Triticum monococcum), one of the earliest domesticated wheat species. Hybridization of a diploid wheat with Aegilops speltoides (a closely…

tetrapod, (superclass Tetrapoda), a superclass of animals that includes all limbed vertebrates (backboned animals) constituting the classes Amphibia (amphibians), Reptilia (reptiles), Aves (birds), Mammalia (mammals), and their direct ancestors that emerged roughly 397 million years ago during the

harbours and sea works: Breakwater design: …most successful has been the tetrapod, a four-legged design, each leg projecting from the centre at an angle of 109 1 2 ° from each of the other three. Legs are bulbous, or pear-shaped, with the slightly larger diameters at the outer end. These units have the property, when placed,…

tetrapod, (superclass Tetrapoda), a superclass of animals that includes all limbed vertebrates (backboned animals) constituting the classes Amphibia (amphibians), Reptilia (reptiles), Aves (birds), Mammalia (mammals), and their direct ancestors that emerged roughly 397 million years ago during the

ancient Greek civilization: The Battle of Marathon: …the Marathonian “Four Cities,” or Tetrapolis, was broken up among more than one of the new tribes. Reasonably or unreasonably, Hippias was obviously hoping to establish a kind of political bridgehead here by appealing to old bonds of clientship.

spearfish, any of certain marine fishes of the genus Tetrapterus, family Istiophoridae (order Perciformes). Spearfishes are characterized by a relatively short snout in comparison with other billfish. Several species may be recognized; two, T. audax and T. albidus, are commonly called marlin

marlin: The white marlin (K. albida, or K. albidus) is limited to the Atlantic and is blue-green, with a paler belly and with pale vertical bars on its sides. Its maximum weight is about 45 kg (100 pounds).

spearfish: The shortbill, or short-nosed, spearfish (T. angustirostris) is a Pacific member of the genus—scarce and rather small for a billfish. Blue above and silvery below, it usually does not exceed 1.8 m (6 feet) and 27 kg (60 pounds). The species T. belone is a Mediterranean…

marlin: The striped marlin (Kajikia audax), another Indo-Pacific fish, is bluish above and white below, with pale vertical bars; it normally does not exceed 125 kg (275 pounds). The white marlin (K. albida, or K. albidus) is limited to the Atlantic and is blue-green, with a paler…

spearfish: The species T. belone is a Mediterranean form resembling T. angustirostris.