Five tribes are considered as belonging to this group of the Siouan linguistic family: Omaha, Ponca, Quapaw, Osage, and Kansa. Distinct from the Dakota-Assiniboin tribes already mentioned, these undoubtedly some centuries ago lived in the central and upper Ohio valleys, whence they moved westward to and beyond the Mississippi. To these tribes may be attributed the great earthworks of the southern portion of Ohio and the adjacent regions bordering the Ohio River. To quote from the Handbook: "Hale and Dorsey concluded from a study of the languages and traditions that, in the westward migration of the Dhegiha from their seat on Ohio and Wabash rivers, after the separation, at least as early as 1500, of the Quapaw, who went down the Mississippi from the mouth of the Ohio, the Omaha branch moved up the great river, remaining awhile near the mouth of the Missouri while war and hunting parties explored the country to the northwest. The Osage remained on Osage River, and the Kansa continued up the Missouri, while the Omaha, still including the Ponca, crossed the latter stream and remained for a period in Iowa, ranging as far as the Pipestone quarry at the present Pipestone, Minnesota." While living in the heavily timbered valleys reaching to the Ohio the several tribes now being considered unquestionably occupied villages consisting of groups of mat-covered lodges of the type erected by the Osage and Quapaw until the present time. But with the Omaha, Ponca, and Kansa, it was different, and when they reached the intermediate region, where forest and prairie joined, they were compelled to adopt a new form of structure, one suited to the natural environments, and thus they began to make use of the earth-covered lodge, and the conical skin tipi, with certain variations in form. The characteristic structures of the five tribes will now be briefly described, beginning with those of the Omaha. OMAHA.