This style of Northwest Coast Native American art is called "formline" design. The term "formline" was coined by Bill Holm in his book Northwest Coast Indian Art: An Analysis of Form. Formline design is characterized by shapes - ovoids, U forms and S forms and adheres to a strict set of rules.
Tlingit Bentwood Box
From The Handbook of North American Indians: Northwest Coast, Volume 7. William Sturtevant, ed. Smithsonian Institution Press, 1991.
Medium: Pen and ink, with film overlays