The zoological collections made by the 1948—1949 Surinam Expedition contain about 200 mammals, brought together by the zoologists Dr. D. C. GEIJSKES and Mr. P. H. CREUTZBERG. Though the collection consists mainly of species which had already been reported from Dutch Guiana, it is of considerable value, in the first place on account of the detailed data concerning the localities, biotopes, and biology, and secondly because not only the skins and skulls of the collected specimens have been preserved but as a rule also their complete skeletons. The present paper ¹) deals with the Primates; the other groups of mammals will be treated in subsequent publications. Thanks are due to Dr. D. C. GEIJSKES, who is responsible for the notes on the biology of the species. The skeletons of the material dealt with here have recently been studied in the Leiden Museum by Mr. G. E. ERIKSON of Harvard Medical School, Boston, who intends to publish the results of his investigation in the near future.