Musculium transversum (Say, 1829): a species new to the fauna of France (Bivalvia, Sphaeriidae)

During a survey of various canals in northern France the bivalve Musculium transversum (Say, 1829) was collected, which species is new to the fauna of France. It inhabits a reach of the lateral canal of the Oise River near Apilly (between Noyon and Chauny). M. transversum, a native of North America, was first recorded from Britain in 1856 and next from the Netherlands in 1954. In the Mississippi River densities may exceed 100,000 per square metre, but in France so far numbers reach only about one hundred per square metre, which may be due to the production of ammonia during the summer. In the Oise R. lateral canal dominant species associated with M. transversum are characteristic of the potamon.