Bull boats

Small, coracle-like vessels used by the Plains Indians.

This image, of a [proabably Mandan] woman paddling a bull boat, is referenced in About Indians: a listing of books as being from E.S. Curtis, The North American Indian (no further details given.)

The following is from The Bark Canoes and Skin Boats of North America by Edwin Tappan Adney and Howard I. Chapelle, Washington 1964: