Boulder mosaics (spelled as bowlder outlines by Hodge). Certain outline surface figures, probably of Siouan origin, usually formed of bowlders a foot or less in diameter, though a few consisted of buffalo bones. The name “boulder mosaics” was first applied to them by Todd. According to Lewis, structures of this type have been found from w. Iowa and Nebraska to Manitoba, and from w. Minnesota through North and South Dakota to Montana; but they appear to be, or rather to have been, more frequent in South Dakota than in any other section. These animal, human, and remains consist of other figures out lined upon the surface of the ground, usually on elevated sites, the human, turtle, and serpent figures being by far the most numerous. In Dakota the out lines are generally accompanied with small stone circles, known to be old tipi sites. In some instances long lines of bowlders or buffalo bones and small stone cairns have been found associated with them or occurring in their immediate neighborhood. Like the bowlder circles these are more or less embedded in the ground, but this does not necessarily indicate great antiquity; indeed, their frequent association with tipi circles seems to denote that they are comparatively recent. The accompanying turtle figure illustrates the type. Among the Crows of Montana a bowlder outline figure is made in the form of a woman to commemorate the unfaithfulness of a wife.
Consult Lewis in Am. Anthrop., n, Apr., 1889, in, July, 1890; Simms, ibid., n. s., v,374, 1903; Thomas in 12th Rep. B. A. E., 534, 1894; Todd in Am. Naturalist, Jan., 1884. (C. T.)