In his valuable report on the freshwater fishes of British Guiana, Eigenmann (1912, pp. 64-73) gave a list of the species, together with comparable lists on the freshwater fishes of the adjacent regions. In sharp contrast with the number of 266 species reported from the Essequibo area only, the total amount of Surinam species proved to be but 118! Although since Eigenmann compiled these lists some more species have been reported from Surinam, the general situation has remained essentially the same, clearly showing the backward state of ichthyological research in this area. A possibility to improve our knowledge of this subject came when during the last four years the Rijksmuseum van Natuurlijke Historie received several more or less extensive collections of fishes from various parts of Surinam, on a small part of which two short reports have already been published (Boeseman, 1948a, b). However, as it was thought advisable to include all Surinam material available, the investigations thereof and the subsequent preparation of a comprehensive report would obviously take several years. On account of this, it was considered useful to published some preliminary results of the investigations on the first part of our still rapidly growing collection of Surinam material. As this publication is meant to be principally of faunistic importance, all species already mentioned in Eigenmann's list (l.c.) have been omitted. Potamotrygon hystrix (Müller & Henle). 1 ex., embryonic, in creek, Coppenam River Trail to Table Mountain (line III), 1st camp at km 57, Emma Range of Mountains, November, 1044, Dr. D. C. Geijskes, total length 23 cm.