DURING investigations of the bacterial decomposition of thiosulphate and thiocyanate in effluents from gasworks, it became necessary to identify the organisms responsible. These were Thiobacilli, and one in particular, organism G, appeared identical with T. thioparus as described in Bergey1. To confirm this, its behaviour was compared with various Thiobacilli from the National Collection of Industrial Bacteria. As a result of this comparison it was discovered that the type species, T. thioparus (NCIB 8370), did not correspond with Bergey's classification on two important points: it grew on nutrient agar, and it grew anaerobically on thiosulphate containing potassium nitrate. To check this a further specimen of the organism was obtained, and although this was again a pure culture it showed precisely the same characteristics.