Tetrahedrite
a name given to a group of minerals having considerable diversity in composition, but presenting the same general general formula. Named from the prevailing tetrahedral habit of its crystals. Crystallization isometric, frequently twinned; luster, metallic; ic; color and streak, steel-gray to iron-black; opaque; fracture, sub-conchoidal, uneven; brittle. Composition, essentially a sulphantimonite of copper, with the formula 4CuS-+Sb2S3; but in consequence of part of the copper being frequently replaced by iron, zinc, silver, mercury, and occasionally cobalt, and part of the antimony by arsenic or bismuth, the general formula is usually written as 4(Cu, Fe, Zn, Ag, Hg)+(Sb, As, Bi) 2S3. Dana divides tetrahedrites as follows: (1) An antimonial series. (2) An arsenio-antimonial series. (3) A bismuthic-arsenioantimonial and an arsenical series, in which the antimony is entirely replaced by arsenic. The varieties are: (1) Ordi nary, containing very little or no silver. (2) Argentiferous = freibergite. (3) schwatzite, spaniolite Mercuriferous = , and hermesite. (4) Platiniferous. Fieldite, aphthonite and polytelite are subspecies. An abundant ore in many parts of the world, sometimes, where rich in silver, mined for that metal only.
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Tetrahedron
or TETRAE- DRON, in geometry, a polyhedron bounded by four triangles. If the middle points of the faces be properly joined, two and two, the lines joining them are the edges of a second tetrahedron. A regular tetrahedron is one in which the faces are equal and equilateral triangles. If the middle points of the faces be joined two and two, the lines joining them form the edges of a regular tetrahedron. All regular tetrahedrons are similar solids.
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Tetralogy
in Greek drama, the name given to a collection of four' dramatic compositions—a trilogy and a satyric piece-exhibited together on the Athenian stage for the prize given at the festival of Bacchus. The expression tetralogy is sometimes applied by modern authors to a series of four connected plays.
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Tetramera
in zoölogy, in Latreille's classification, a section of the Coleoptera. They are distinguished by the atrophy of the fourth tarsal joint in all the feet, so that they have only four freely articulating joints. The atrophied joint is generally extremely minute, and concealed in the deep notch of the third joint, which, in the majority of the species, is bilobed and clothed beneath with a brush of minute hairs. The section includes more than a third of the whole order, and all the species are vegetable feeders.
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Tetraonine
a typical sub-family of the Tetraonidæ, chiefly from the N. parts of the Palearctic and Nearctic regions, with the following genera: Tetrao, Bonasa, Centrocercus, Dendragopus, Canace, Falcipennis, Pediocætes, Cupidonia, and Lagopus. They are rather large in size, heavy in body, with small heads, the nasal fosse filled with feathers concealing the nostrils; neck moderately long; wings short, rounded, and concave beneath; stout legs and feet; toes with pectinations of scales along the edges, hind toe elevated above the plane of the rest; tarsi covered with feathers, in Bonasa partially, in Lagopus, to the claws.
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Tetraonyx
in zoology, an Asiatic genus of Emydæ, having hav five toes, but one on each foot without a nail. Twentyfive marginal scales. Species, T. lessonii and T. baska.
in zoology, an Asiatic genus of Emydæ, having five toes, but one on each foot without a nail. Twentyfive marginal scales. Species, T. lessonii and T. baska.
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Tetrastyle
in architecture, having or consisting of four columns; having a portico consisting of four columns; as the Temple of Fortuna Virilis at Rome; a portico, etc., consisting of four columns. A cavædium was called tetrastyle when the beams of the compluvium were supported by columns placed over against the four angles of a court.
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Tetrazzini
LUISA, an Italian widely dispersed throughout the world, but abounding chiefly in the northern temperate and subtropical regions of the Eastern Hemisphere. They are called germanders. Several species were formerly reputed to possess medicinal virtues, but are now discarded. The genus is represented in North America by T. Canadense, the wild germander, about two feet high, found in fields and roadsides throughout the United States.
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Tetrodon
or TETRAODON, in ichthyology, the type genus of Tetrodon tina, having the upper and lower jaws divided by a mesial suture, so as to separate the dentition into four distinct portions. More than 60 species are known, from tropical and sub-tropical seas. some the dermal spines are extremely In small, and may be absent altogether, and many of them are highly ornamented with spots or bands. A few live in large rivers; as, T. psittacus, from Brazil; T. fahaka, from the Nile and West African rivers, and T. fluviatilis, from brackish waters and rivers of the East Indies.
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Tetrolic Acid
C4H4O2; a monobasic acid prepared by heating chlor alpha crotonic acid with alcoholic potassic hydrate on the water-bath, decomposing the potassium salt formed with sulphuric acid, and extracting with ether. It crystallizes in rhombic tables, soluble in alcohol and ether, melts at 76.5°, and boils at 203°. Africa, in the province of El Garb; on
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Teucrium
a genus of plants, order Lamiaceæ, consisting of herbs and shrubs
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Teudopsis
in paleontology, a genus of Teuthidæ, or a sub-genus of Loligo, with five species, from the Upper Lias and Oölite of France and Württemberg. Pen like the Loligo, but dilated and spatulate behind.
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Teuffel
WILHELM, a German philologist; born in Ludwigsburg, Germany, Sept. 27, 1820. His greatest work is the "History of Roman Literature" (1870). He wrote also: "Exercises in Latin Style" (1887); "Studies in Greek and Roman, and also in German Literary History" y" (1871); ; and edited with notes several Greek and Roman classics. He died in Tübingen, where he was professor in the university, March 8, 1878.
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Teutates
in mythology, a deity mentioned by Lucan as being worshipped with sacrifices not unlike those of Moloch.
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Teuthide
in zoölogy, calamaries, or squids; a family of dibranchiate Cephalopods, section Octopoda. Body elongated; fins short, broad, and mostly terminal; shell horny, consisting of a shaft and two lateral expansions or wings. There are 18 genera, very widely distributed, which D'Orbigny divided into two sub-families: Myopsidæ (having the eyes covered with skin) and Oigopsidæ (having the eyes naked, fins terminal and united, forming a rhomb).
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