The fauna of Olduvai is now represented by very extensive collections found in situ in Beds I and II. These are supplemented by material collected on the surface or excavated from exposures when the fossils had become visible as a result of erosion. These collections will require many years of work before the final reports can be published. This is partly because many specimens have to be sent to specialists all over the world and partly because the quantity of material in certain groups is very great indeed. In the present volume it is possible to give only a summary, but this will present a clearer picture of the fauna of Olduvai than has been possible in the past.

In this and the next two chapters, only the families, subfamilies and genera are given in some cases, since the detailed work has not yet been carried out. In other groups, such as the Bovidae and the Suidae, a more complete picture is given, with diagnoses and descriptions of new genera and species, where possible. Material which had previously been inadequately described is dealt with a little more fully and is illustrated. In a few cases the quantity of material is so great, as for example in the genera Pelorovis and Bularchus, that no attempt has been made to discuss it in detail for the time being.

In this chapter, various scientists have collaborated to present a preliminary statement, and I am most grateful to them.