In the Baltic Provinces the succession is mainly of shallow water type, and affords perhaps the best development of the rocks of that type recognized in Europe. The succession presents some striking analogies with that of the Scandinavian shallow-water de velopment of which it is no doubt the counter part on the southern shore line; hence the Vaginatenkalk and Echinosphaerite Kalk show many features in common with the Orthoceras Limestone and Cystid Limestone of the northern region. It does not appear pos sible however, to correlate exactly the beds that are said to overlie the Echinosphaerite Kalk, namely the Jewe Itfer, and Kuckers Schiefer, beyond the fact that they appear to belong to the Upper Ordovician.
At the base of the Ordovician succession in Bohemia, there is an unconformity of considerable importance so that the basal beds are naturally of a littoral character (Dia) ; above, Grapto lite Shales of Arenig age occur, and the beds of Llanvirn age (DO) contain a mixed fauna of trilobites and graptolites; the remainder of the succession is formed a richly fossiliferous shal low-water series of sandstones and shales representing everything III up to the top of the Ashgillian.
North America.—In the geosynclinal areas of North America, both shallow water and deeper water facies of deposit are found and these are often highly disturbed by the movements in which they have been involved since their deposition; outside these geosynclinal areas the beds show very little signs of any disturb ance, are thinner and consist very largely of calcareous beds with different varieties of shallow water faunas.
The Graptolite Shale facies is best known in the area belonging to the Appalachian geosyncline, but includes also beds now lying outside it in the St. Lawrence valley which have probably been brought by thrusting into their present position. The classic de
velopment of the Graptolite Shale facies of the Lower Ordovician is that known as the Levis Shales of the Quebec group seen on the south shore of the St. Lawrence immediately opposite Quebec; the remainder of the Graptolitic facies is best known from New York State where they form the Hudson river Shales of Albany. The shallow water facies is found extensively in the north in the Hud son bay region (Manitoba, Hudson bay and the Arctic archipel ago), and in the south or Mississippean region along the margins of the Canadian shield in Michigan, Wisconsin and Minnesota, and on the domes of Cincinnati and Nashville.
Australia.—In Australia the same three facies of the Ordovician are characteristically developed. Beds belonging to the shallow water facies have only up to the present been definitely recorded along the east to west line in Northern Territory in the heart of the continent (Tempe Downs, and Levi Range, south of the Mac Donnell Ranges) the dominant type, which is found mainly in the eastern half of the continent, belonging to the Graptolite Shale facies; these are best seen in Victoria where the Lower Ordovician rocks of this type have become well known through their occur rence in the most productive gold field ; Upper Ordovician of simi lar type, though less auriferous, occur east of a line running north from Melbourne, and are also found in New South Wales. Vol canic rocks of the age have an extensive development in central New South Wales and in Tasmania (see AUSTRALIA). (G. L. E.) ORDU (anc. Cotyora, where the "Ten Thousand" embarked for home), the chief town of a vilayet, on the north coast of Asia Minor, between Samsun and Kerasund, connected with Zara, and so with Sivas, by road, and with Constantinople and Trebizond by steamer. Filberts are exported. Pop. (1927), 113,004.