The material discussed in this paper was obtained during 1966 from the region to the west of Lake Baringo. Excavations were conducted in two areas about a mile apart, on either side of the Kapthurin River. The positions of these excavations are to be found on the 1: 50,000 Survey of Kenya map, Sheet 90/4 of Series Y731, Edition I-D.O.S. The first is located at ZR 314/637 and the second at ZR 316/621. Fig. 1 is based on a small section of Sheets 30/4 and 31/3 and is reproduced by permission of the Director of Surveys, Nairobi. A hominid mandible and a living site were discovered in the first area whilst in the second a factory site was found. These sites lie in the Kapthurin Beds of the eastern area of the Kamasian Hills. The beds are possibly upper Middle Pleistocene and are divided from the underlying Chemeron beds which are of Plio/Pleistocene age. The geology of the area was first described by J. W. Gregory (1921). It was subsequently studied and re-assessed by V. E. Fuchs (1939 and 1950) and by McCall, Baker and Walsh (1967). The most recent study has been made by Mr J. E. Martyn of Bedford College, London, who was engaged in geological mapping of the area west of Lake Baringo in 1966 and 1967. A report on the Kapthurin Beds by J. E. Martyn follows this introduction. During the course of mapping, J. E. Martyn and his assistants found a number of fossils in the Chemeron beds. He showed these to Mr Jonathan Leakey who noticed an incomplete hominid temporal bone amongst them.
