Three new ostracod species, each belonging to a new genus, were described by the first author (DE VOS, 1953). They had been found on the body and the legs of Limnoria lignorum, the well-known woodburrowing isopod. Since then, we have been looking for commensals in several new lots of European Limnoria, and in this way we obtained valuable new data on morphology and distribution of two of the three ostracod species described. Moreover, Dr. Robert I. MENZIES, La Jolla, California, kindly sent us a beautiful lot of ostracods from Limnoria tripunctata MENZIES, an isopod species from the Pacific coast of America, found in test-blocks placed at about 7 feet below mean tide level, and collected in the course of the marine wood-borer studies, Project NR 163—084 at the Scripps Institution of Oceanography, which is supported by the U.S. Office of Naval Research.