As shown on Powell’s map, the chief part of the Siouan area comprised a single body covering most of the region of the Great plains, stretching from the Rocky mountains to the Mississippi and from the Arkansas-Red river divide nearly to the Saskatchewan, with an arm crossing the Mississippi and extending to Lake Michigan. In addition there were a few outlying bodies, the largest and easternmost bordering the Atlantic from Santee river nearly to Capes Lookout and Hatteras, and skirting the Appalachian range northward to the Potomac; the next considerable area lay on the Gulf coast about Pascagoula river and bay, stretching nearly from the Pearl to the Mobile; and there were one or two unimportant areas on Ohio river, which were temporarily occupied by small groups of Siouan Indians during recent times. There is little probability that the Siouan habitat, as thus outlined, ran far into the prehistoric age. As already noted, the Siouan Indians of the plains were undoubtedly descended from the Siouan tribes of the east (indeed the Mandan had a tradition to that effect); and reason has been given for supposing that the ancestors of the prairie hunters followed the straggling buffalo through the cis-Mississippi forests into his normal trans-Mississippi habitat and spread over his domain save as they were held in check by alien huntsmen, chiefly of the warlike Caddoan and Kiowan tribes; and the buffalo itself was a geologically recent—indeed essentially post-glacial—animal. Little if any definite trace of Siouan occupancy has been found in the more ancient prehistoric works of the Mississippi valley. On the whole it appears probable that the prehistoric development of the Siouan stock and habitat was exceptionally rapid, that the Siouan Indians were a vigorous and virile people that arose quickly under the stimulus of strong vitality (the acquisition of which need not here be considered), coupled with exceptionally favorable opportunity, to a power and glory culminating about the time of discovery. ORGANIZATION The demotic organization of the Siouan peoples, so far as known, is set forth in considerable detail in Mr Dorsey’s treatises(52) and in the foregoing enumeration of tribes, confederacies, and other linguistic groups. Like the other aborigines north of Mexico, the Siouan Indians were organized on the basis of kinship, and were thus in the stage of tribal society. All of the best-known tribes had reached that plane in organization characterized by descent in the male line, though many vestiges and some relatively unimportant examples of descent in the female line have been discovered. Thus the clan system was obsolescent and the gentile system fairly developed; i. e., the people were practically out of the stage of savagery and well advanced in the stage of barbarism.