Page:Collier's New Encyclopedia v. 09.djvu/371

TETRAHEDRON 319 TETUAN 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 tetra- hedron. All regular tetrahedrons are similar solids. TETRALOGY, in Greek drama, the name given to a collection of four dra- matic compositions — a trilogy and a saty- ric piece — exhibited together on the Athe- nian stage for the prize given at the festival of Bacchus. The expression tet- ralogy is sometimes applied by modern authors to a series of four connected plays. TETRAMERA, in zoology, 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 spe- cies, 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. TETRAONIN^, a typical sub-family of the Tetraonidx, chiefly from the N. parts of the Palasarctic and Nearctic re- gions, with the following genera : Tetrao, Bonasa, Centrocercus, Dendragopus, Ca- nace, Falcipennis, Pediocsetes, Cupidonia, and Lagopus. They are rather large in size, heavy in body, with small heads, the nasal fossae filled with feathers con- cealing 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. TETRAONYX, in zoology, an Asiatic genus of Emydse, having five toes, but one on each foot without a nail. Twenty- five marginal scales. Species, T. lessonii and T. baska. TETRAOPHASIS, in ornithology, the Lophophorus obscurus; often made a separate genus of the sub-family Lopho- phorinse, connecting the PJutsianinx with Tetraogallus, and so with the Perdicinse. This bird was discovered by Pere David in Tibet and described by him. General color brown, marked with darker shades ; bare skin of face red, tarsi and feet horn- color. The sexes are alike in plumage; female destitute of spurs. TETRARCH ("governor of the fourth part," i. e., of a country), a title original- ly designating what is signified by its etymology, the governor of one of four divisions of a kingdom or country; but in the usage of the later Roman empire given undistinguishingly to all minor rulers, especially in the E., possessing sovereign right within their territory, but dependent on the emperor, and in many cases removable at his pleasure. This was especially the case in Syria, where the princes of the family of Herod are called indiscriminately by this title (Luke iii: 1) and by that of king (Matt, xiv: 9). TETRASTYLE, in architecture, hav- ing or consisting of four columns; hav- ing a portico consisting of four columns; as the Temple of Fortuna Virilis at Rome; a portico, etc., consisting of four columns. A cavsedium was called tetra- style when the beams of the compluvium were supported by columns placed over against the four angles of a court. TETRODON, or TETRAODON, in ich- thyology, the type genus of TetrodoTU titm, having the upper and lower jaws divided by a mesial suture, so as to sepa- rate the dentition into four distinct por-. tions. More than 60 species are known, from tropical and sub-tropical seas. In some the dermal spines are extremely 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. TETROLIC ACID, C4H4O2; a mono- basic acid prepared by heating chlor al- pJwb crotonic acid with alcoholic potassic hydrate on the water-bath, decomposing the potassium salt formed with sulphuric acid, and extracting with ether. It crys- tallizes in rhombic tables, soluble in al- cohol and ether, melts at 76.5°, and boils at 203°. TETUAN, a seaport town of Morocco, Africa, in the province of El Garb; on the Mediterranean, immediately within the Straits of Gibraltar, 22 miles from Ceuta. The environs are carefully plant- ed with vineyards and gardens; the grapes are exquisite, and the oranges reckoned, by some, superior to any in the world. In 1861 the Spanish government, having determined to abandon its claims against Morocco, declared Tetuan the property of Spain, rendered it impreg- nable, and colonized its territory. The exports are wool, silk, cotton, leather, etc. Pop. about 25,000.