The collections of the South American Nematognathi in the Rijksmuseum van Natuurlijke Historie at Leiden, referred to in this publication as "Museum Leiden", and of those in the Zoölogisch Museum at Amsterdam, referred to as "Museum Amsterdam", consist of valuable material, which for a very important part has not been studied yet. I feel very much obliged to Prof. Dr. H. Boschma who allowed me to start with the study of the Leiden collections and whom I offer here my sincere thanks. At the same time I want to express my gratitude towards Prof. Dr. L. F. de Beaufort, who has been so kind to place the collection of the Zoological Museum at Amsterdam at my disposal. Furthermore I am greatly indebted to Dr. F. P. Koumans at Leiden for his assistance and advice to solve the various problems which I met during my study. The material dealt with here comes from a large number of collections of different collectors, from various areas of South America, it consists of 125 species, belonging to 14 families of the order Nematognathi. Contrary to the original expectations no adequate number of specimens from Surinam could be obtained to get a sufficient opinion about the occurrence of the various species, and, if possible, also about their distribution in this tropical American part of the Netherlands. On the whole the collections from Surinam were limited to the generally known species only. Pygidium gracilior Eigenm., hitherto not known from Surinam, forms an exception in this respect. Out of the 125 species described in the present paper only 41 originate from Surinam. At the beginning of Bleeker's (1864) investigations of the Nematognathi in the collections of the Museum Leiden and the Museum Amsterdam, there were 23 species from Surinam. During