ICONOSTASIS, the screen in a Greek church which divides the altar and sanctuary from the rest of the church. It is generally attached to the first eastern pier or column and rises to the level of the springing of the vault. The iconostasis or image-bearer has generally three doors, one on each side of the central door, beyond which is the principal altar. The screen is subdivided into four or five tiers, each tier decorated with a series of panels containing representations of the saints: of these only the heads, hands and feet are painted, the bodies being covered with embossed metal work, richly gilded. There is a fine example in the Russo-Greek chapel, Welbeck Street, London, which was rebuilt in 1864-1865. ICOSAHEDRON (Gr. [Greek: eikosi], twenty, and [Greek: hedra], a face or base), in geometry, a solid enclosed by twenty faces. The "regular icosahedron" is one of the Platonic solids; the "great icosahedron" is a Kepler-Poinsot solid; and the "truncated icosahedron" is an Archimedean solid (see POLYHEDRON). In crystallography the icosahedron is a possible form, but it has not been observed; it is closely simulated by a combination of the octahedron and pentagonal dodecahedron, which has twenty triangular faces, but only eight are equilateral, the remaining twelve being isosceles (see CRYSTALLOGRAPHY). ICTERUS, a bird so called by classical authors, and supposed by Pliny to be the same as the _Galgulus_, which is generally identified with the golden oriole (_Oriolus galbula_).[1] It signified a bird in the plumage of which yellow or green predominated, and hence Brisson did not take an unhappy liberty when he applied it in a scientific sense to some birds of the New World of which the same could be said. These are now held to constitute a distinct family, _Icteridae_, intermediate it would seem between the BUNTINGS (q.v.) and STARLINGS (q.v.); and, while many of them are called troopials (the English equivalent of the French _Troupiales_, first used by Brisson), others are known as the American GRACKLES (q.v.). The typical species of _Icterus_ is the _Oriolus icterus_ of Linnaeus, the _Icterus vulgaris_ of Daudin and modern ornithologists, an inhabitant of northern Brazil, Guiana, Venezuela, occasionally visiting some of the Antilles and of the United States. Thirty-three species of the genus _Icterus_ alone, and more than seventy others belonging to upwards of a score of genera, are recognized by Sclater and Salvin (_Nomenclator_, pp. 35-39) as belonging to the Neotropical Region, though a few of them emigrate to the northward in summer. _Cassicus_ and _Ostinops_ may perhaps be named as the most remarkable. They are nearly all gregarious birds, many of them with loud and in most cases, where they have been observed, with melodious notes, rendering them favourites in captivity, for they readily learn to whistle simple tunes. Some have a plumage wholly black, others are