Hal Walker was a National Geographic Society photographer and writer who reported on the 1948 American-Australian Scientific Expedition to Arnhem Land for the Society. He published his account in 1949 as 'Cruise to Stone-age Arnhem Land'.

The photograph beneath features Mountford's guide, Marawana, also known as 'Larry', in front of some of the paintings of Mimi figures found amongst the caves and cliffs of Injalak Hill.

Mimis are good spirits that live in rocks, caves, trees and water, but are rarely, if ever seen. Some believe they are also the creators of these paintings. Indeed they are older, and in start contrast to the artistic style of the x-ray art also found in and around Oenpelli, believed to be painted by either the Mangaridji or Kakadu people who previously inhabited the area.

Painted in red ochre, Mimis are usually depicted as highly animated - dancing, hunting, running and fighting.

American-Australian Scientific Expedition to Arnhem Land, (1948). Records of the American-Australian scientific expedition to Arnhem Land, Melbourne : Melbourne University Press, 1956-1964

Berndt, Ronald M. and Catherine H. Man, land & myth in North Australia : the Gunwinggu people, Sydney : Ure Smith, 1970

Berndt, Ronald M. and Phillips, E. S. (eds). The Australian Aboriginal heritage : an introduction through the arts, 2nd ed, Sydney : Australian Society for Education through the Arts in association with Ure Smith, 1978

Cole, Keith. A history of Oenpelli, Darwin : Nungalinya Publications, 1975

Hamby, Louise (ed). Twined together = kunmadj njalehnjaleken, Gunbalanya, N.T. : Injalak Arts and Crafts, 2005

National Geographic Magazine, vol. 96, no. 3, 1949, pp. 417-430, 'Cruise to Stone-age Arnhem Land' by Howell Walker.

Simpson, Colin, Adam in ochre : inside Aboriginal Australia, 5th ed, Sydney : Angus & Robertson, 1962