INTRODUCTION Since April 1972 an ecological trawl-survey programme has been undertaken by the Netherlands Institute for Sea Research (NIOZ), Texel, in the southern North Sea with the R. V. "Aurelia". The main object is to obtain information on distribution, density, biomass and fluctuations of crawling or swimming demersal (epibenthic) fauna such as small fishes, shrimps, prawns, crabs, asteroids, ophiuroids and some gastropods, for the evaluation of the role of these carnivores in the benthic ecosystem of the southern North Sea. Sedimentological aspects of the area are described by Creutzberg & Postma (1979). Within the context of the present paper the most important feature is the mesh of 5 x 5 mm2 of the cod end of the 51/2 m beam-trawl used and the extensive area of 5000-10,000 m2 covered during each haul. These exceptional circumstances resulted into faunistically interesting catches which gave rise to a cooperation with taxonomic specialists of the Rijksmuseum van Natuurlijke Historie (RMNH), Leiden. The present paper deals with decapod crustaceans, collected during "Aurelia"-cruises, which are considered to be scarce or rare in the southern North Sea, completed with data from bottom-samples and other sources. The species in question are: Pandalina brevirostris, Spirontocaris lilljeborgii, Alpheus macrocheles, Pontophilus spinosus, Pontophilus bispinosus, Galathea dispersa, Ebalia tuberosa, Ebalia tumefacta, Ebalia cranchii, Atelecyclus rotundatus, Monodaeus couchii, Callianassa subterranea, Callianassa tyrrhena, Upogeb ia stellata and Upogebia deltaura. Of the genus Macropodia a number of specimens have been collected, which partly were identified as M. linaresi. Other specimens, however, represent one or two new species. On Macropodia in the southern North Sea a seperate paper will